• A graph that is parallel to velocity axis, is perpendicular to time axis.
• Thus, if the graph is parallel to velocity axis, then we can say that at a particular instant of time, the velocity increases from some initial value to a final value.
• This means that the velocity change occurs at same time and hence the slope of the graph will be infinity. Thus, the acceleration of the body is infinite.
• This is physically not possible.

AIDS causing virus HIV that comes into the body via the sexual organs or blood transfusion will spread all over the body through lymph nodes. The virus damages the immune system of the body and due to this the body can no longer fight off many minor infections. Instead, every small disease like cold can become severe pneumonia or minor gut infection can become severe diarrhoea with blood loss. The effect of disease becomes very severe and complex, at times killing the person suffering from AIDS. Hence, there is no specific disease symptom for AIDS but it results in a complex disease. Therefore, it is known as a syndrome.

• Ice is a solid but it floats on water because it has low density as compared to water.
• The density of ice is very low as it has tiny pores present in it which traps the air and allow ice to float in water.

Minerals are the largest component in the soil, making up almost 40% to 45% of the total components. The minerals in the soil are classified into two categories, namely

• Primary Minerals in soil: These are minerals which have not been chemically altered since deposition. They are same or similar to their parent materials. Often these materials are bigger in size and irregular in shape. These primary minerals are usually found in sand and silt.
• Secondary Minerals in soil: These are minerals formed as a result of weathering of Primary Minerals. Secondary minerals are mainly found in fine silt or clay. The particle size of these minerals is much smaller, due to the weathering process. These minerals have a large surface area that helps them retain moisture.

We can examine the plant whether it is monocot or dicot on the basis of their structure of seeds, roots , leaves and stems.

Seeds: A seed of a monocot plant has one cotyledon and that of a dicot plants has two cotyledons.

Roots: Monocots have adventitious roots, whereas dicots have a radicle from which a root develops.

Leaves: If the leaf has a stalk, then the plant is a dicot. But, in the case of a monocot plant, the leaf is sessile, which means it is attached directly by its base without a stalk.

Leaves venation: If the leaves have parallel venations that are long and thin, then the plant is monocot. If the leaves have a branched venation, then the plant is a dicot.

Stem: Monocot plants normally have a weak stem, whereas dicots have a strong stem.

• The process by which huge rocks are broken down into small particles by the action of sun’s heat, wind, rain and flowing river water etc. is called weathering.
• The vertical section through the soil showing the different layers of soil is called soil profile.

Soil is composed of distinct layers. The rotting matter in the soil is called humus. A vertical section through the soil showing the different layers of soil is called soil profile.

The noble gases are the least reactive out of all the elements because each one has a full valence shell (8 electrons in outer shell), which is the most stable arrangement of electrons for an atom. They are satisfied with their 8 electrons and do not feel the need to react with other atoms to “fill the shell” to attain stability as others do.

If an object changes its position with respect to a reference point with elapse of time, the object is said to be in motion. To observe the motion of any object; two things are necessary – a reference point and time.

Because it surrounds the earth just like a blanket

• The layers of the atmosphere help protect the earth, like a blanket.
• The ozone layer protects the Earth from dangerous UV rays from the sun
• The atmosphere prevents meteors from striking the Earth.
• The atmosphere also keeps what helps us stay alive inside of the Earth, for example oxygen.
• The greenhouse gases in the atmosphere absorb the sun's heat, radiated from the surface of the earth, and keep the planet warm enough for life.

Animal husbandry is the science of farming of animal livestock. It includes caring, breeding and management of livestock. Animal husbandry is a large scale business where animals that provide us food are reared, bred, sheltered and cared in a farm or regions which are specially built for them.  Animal husbandry was initiated with cattle farming. Under the cattle farming, livestock such as cows, goats, buffalo, sheep, etc. are reared.
Advantage of Animal husbandry

1. Animal husbandry helps us in providing proper feed, proper shelter and protection against diseases to the domestic animals. Thus, animal husbandry helps in proper management of the domestic animals.

2. Animal husbandry helps us in developing high yielding breeds of various domestic animals through cross breeding. Thus, animal husbandry increases the availability of various food products such as milk, eggs and meat, which are obtained from domestic animals.

3. Animal husbandry helps in raising the living standard of farmers. As a result of higher production of animal products, the income of farmers increases.

4. Animal husbandry helps in systematic disposal of animal wastes. Thus, it helps in maintaining healthy environment.