Economic activities are broadly grouped as Primary activities, Secondary activities, Tertiary activities and Quaternary activities.

1. Primary Activities: It refers to extraction/utilisation of raw materials from the earth's surface. These include hunting, gathering, pastoralism, fishing, forestry, mining and agriculture.
2. Secondary Activities: It includes industries that transform raw materials into finished foods having higher value. For example, manufacturing cotton textiles from raw cotton, and iron and steel from iron ore.
3. Tertiary Activities: It includes all kinds of services provided for the people such as education, health, trade and transport.
4. Quaternary Activities: It represents special kind of services, which is related to highly intellectual activities. For example, research and development service, information generation, information processing and transmission.

Molecular mass of CO₂ = Atomic mass of C + 2 {tex}\times{/tex} Atomic mass of O
= (12u + 2 {tex}\times{/tex} 16u) = 44u
Gram molecular mass of CO₂ = 44 g
1 gram molecule of CO₂ = 44 g
0.72 gram molecule of CO₂ {tex} = \frac{{\left( {44g} \right)}}{{\left( {1g} \right)}} \times \left( {0.72g} \right) = 31.68g{/tex}

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अर्थशास्त्र सामाजिक विज्ञान की वह शाखा है, जिसके अन्तर्गत वस्तुओं और सेवाओं के उत्पादन, वितरण, विनिमय और उपभोग का अध्ययन किया जाता है।

The narrator, a 37-year-old businessman was a lover of adventure. He had dreamt of going around the world sea voyage. He and his wife had spent all the leisure hours for 16 years developing and improving their skills about work or travel on the sea. This shows his love for perfection and attention to details.
The narrator was practical in his approach. He engaged two crewmen to help them sail through the rough waters of the southern Indian Ocean. He had keen foresight. They made advance preparations to protect the ship and passengers against violent sea-storms. He did not lose hope, calm or courage in the face of difficulties. He had his priorities fixed. Repairing the damaged ship was essential. Everything else including injuries could wait. He was resourceful also. He managed to steer the course with the help of whatever had been left with them. His presence of mind helped them to overcome troubles. He had a level head. He made exact calculations of their positions and that of the island. He fixed the course and speed. His self-confidence and practical knowledge made him a good captain.

She was quite an old lady. She had been old and wrinkled for more than two decades. It is said that once she had been young and pretty. But it is hard to believe so.

Atomic radius is defined as the distance from the centre of the nucleus of atom to the outermost shell of electrons.

The development of writing:
(i) The first Mesopotamian tablets, written around 3200 BCE, contained picture-like signs and numbers. These were about 5,000 lists of oxen, fish, bread loaves, etc. - lists of goods that were brought into or distributed from the temples of Uruk, a city in the south.
Clearly, writing began when society needed to keep records of transactions -because in city life transactions occurred at different times, and involved many people and a involved many people and a variety of goods.
(ii) Mesopotamians wrote on tablets of clay. A scribe would wet clay and pat it into a size he could hold comfortably in one hand. He would carefully smoothen its surfaces.
With the sharp end of a reed cut obliquely, he would press wedge-shaped (‘cuneiform) signs on to the smoothened surface while it was still moist. Once dried in the sun, the clay would harden and tablets would be almost as indestructible as pottery. When a written record of, say, the delivery of pieces of metal had ceased to be relevant, the tablet was thrown away.
(iii) Once the surface dried, signs could not be pressed onto a tablet : so each transaction, however minor, required a separate written tablet.
This is why tablets occur by the hundreds at Mesopotamian sites. And it is because of this wealth of sources that we know so much more about Mesopotamia than we do about contemporary India.
(iv) By 2600 BCE or so, the letters became cuneiform, and the language was Sumerian. Writing was now used not only for keeping records, but also for making dictionaries, giving legal validity to land transfers, narrating the deeds of kings, and announcing the changes a king had made in the customary laws of the land.
Sumerian, the earliest known language of Mesopotamia, was gradually replaced after 2400 BCE by the Akkadian language. Cuneiform writing in the Akkadian language continued in use until the first century CE, that is, for more than 2,000 years.

India, the biggest democracy in the world, is condemned for its easy attitude towards laws. Laws are constituted but never respected nor enforced in our country. For instance, the Indian Constitution mentions that casteism, untouchability and bonded labour shall be abolished; however, these evils flourish barefacedly even today.
The author points out that Article 48A of the Indian Constitution propounds that “the State shall endeavor to protect and improve the environment and to safeguard the forests and wildlife of the country”. However, little is done in favour of this. What we see is a near “catastrophic depletion” of forests over the last four decades. Forests are disappearing over the decades at the rate of 3.7 million acres a year. Areas that are officially designated as forest land, in reality, are treeless. The actual loss of forests is eight times the rate pointed by the government statistics.

a) The angiosperms are the dominant group of land plants. These are the most common flowering plants.
b) The angiosperms are seed bearing plants and the seeds are enclosed inside the fruit formed from ovary.
c) Carpel is like of megasporophyll as gymnosperms, but it is differentiated ovary, style and stigma
d) The pollen grain is received by the stigma causing pollination.
e) Ovary develops into fruit and ovules into seeds after the act of fertilization.

Prior to the adoption of agriculture, people had gathered plant produce as a source of food. About 160,000 years ago, people obtained food by either scavenging or hunting animals and gathering plant produce. They also learnt how to make stone tools and to communicate with each other. Although other ways of obtaining food were adopted later, hunting-gathering continued.

Physical education is a course taught in school that focuses on developing physical fitness.
Objectives of Physical Education are : 

1. Physical development:- Development of organ systems such as circulatory system, nervous system, muscular system, digestive system etc.
2. Mental development:- Physical activities require alertness of mind, deep concentration and calculated movement. This objective is related to the mental development of an individual.
3. Social development:- This objective is related to the development of social traits, which are essential for better adjustment in life. it is a better source for attaining the qualities like. Co-operation, fair play, sportsmanship tolerance and sympathy.
4. Neuro Muscular Co-ordination:- This objective is centered with a better relationship between nervous system. Education provide ample opportunities of physical neuromuscular coordination.
5. Emotional Development:- The emotional development of an individual is also the major objectives of physical education every individual has various types of emotions viz. Pleasure, hope, jealously, hateredness, fear, depression, anger, wonder, lust loneliness etc.
6. Development of Health: This develops health related habits through health education. This also provides education about the prevention of communicable disease.

Criticism is the expression of disapproval of someone or something on the basis of perceived faults or mistakes.

 7.4 to a pH of about 6 in the urine.

Systematics is the study of the units of biodiversity.
Systematic errors are those errors which arises due to the repetition of same values due to fault im instruments. These errors tends to be in one direction either positive or negative.