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.
Causes of systematic errors are:
i) Instrumental errors : These errors occurs due to imperfect design or callibration of measuring instruments.
ii) Imperfect experimental technique or procedure
iii) Personal errors: These errors occurs due to the lack of proper setting of apparatus or observer's carelessness while taking observations.

Preparation :
When we heat baking soda then hydrogen gas released and sodium carbonate left.
When water is added to sodium carbonate then it becomes washing soda.
Equation :
2Nahco3 = Na2CO3 +h2O+co2
Na2CO3 +10h2O =Na2CO3.10H2O

In the 'direct personal investigation', the investigator collects data personally while in the 'indirect oral investigation', the data are collected from indirect resources.
Difference between 'direct personal investigation' and 'indirect oral investigation':

Direct personal investigation:

1. In this investigation, the data collected is original in manner.
2. The field of the investigation will be limited
3. The information is highly reliable.

Indirect oral investigation:

1. In this investigation, the method of collecting data may lead to false conclusions.
2. The field of investigation can be large.
3. The information can be wrong or biased.

The term ‘business risk’ refer to the possibility of inadequate profits or even losses, due to uncertainties or unexpected events. For example, the demand for a particular product may decline due to change in tastes and preferences of consumers. Decrease in demand will result in lesser sale and thereby lesser profits.
Nature of business risk : The nature of business risks can be understood in terms of its peculiar characteristics:

1. Business risks arise due to uncertainties.
2. Risk is an essential part of every business.
3. Degree of risk depends mainly upon the nature and size of business.
4. Profit is the reward for risk taking.

Effects of Exercises on Muscular System : Following changes in our muscular system can be seen if exercises are done on regular basis :

1. Efficiency in the Movements of Muscles.
   The movements of muscles become efficient and smooth. The movements during different activities become attractive.
2. Change in the Connective Tissue. The connective tissue, which connects fibres, becomes powerful. These tissues can bear stress of strenuous activity and can be extended up to some degree.
3. Controls Extra Fat. Regular exercise controls the extra fat of body. Exercises burn the calories which is taken in the form of fat.
4. Musele Remains in Tone Position. When exercises are done on regular basis then our muscles remain in toned position. Indeed, muscle remains under some degree of contraction. Muscle becomes firm and maintains a slight, steady pull on the attachments.
5. Formation of More Capillaries. When exercises are done, the colour of muscles is changed, because a number of new capillaries are formed for a better efficiency of blood circulation.
6. Change in Shape and Size of Muscle. Through regular exercise, the shape and size of muscle is changed. In fact, cells of muscles are enlarged which change the shape and size of muscle.
7. Delays Fatigue. Regular exercise delays fatigue. The fatigue is mainly due to formation of carbon dioxide, lactic acid and acid phosphate. The accumulation of C02 acid phosphate and lactic acid becomes less in an individual who performs exercise regularly, Hence, fatigue can be delayed if exercises are performed daily.
8. Improves Reaction Time. Due to regular exercise, the speed of nerve impulses increases which ultimately improves the reaction time. These nerve impulses move very quickly through motor nerves from nervous system to muscle fibre. Owing to this the reaction time improves.
9. Body Posture Remains Correct. By doing exercise regularly, the strength of muscles increases, which in turn, keeps the body posture in correct position. The postural deformities do not occur. If there is any physical deformity, it is removed by doing regular exercise.
10. Non-functioning Fibres Become Active.
    When we do not do any strenuous work, all the muscle fibres of our body do not perform any work. In fact, these fibres do not need to be active. But when we perform exercise regularly, the non-functioning fibres also begin to be active. Consequently, the strength of the body increases, because the total contractile power of the muscle fibres increases.

A person or any group of people, who look up to and aspire to be like someone. • Person or groups whose lifestyles are emulated. • We do not belong to a reference group, but we do identify ourselves with that group. • Reference groups are important sources of information about culture, life style, aspiration and goal attainments

a) A Bill of Rights lays down the rights enjoyed by the people of a country.

b) A Bill of Rights protects the liberties of an individual.

c) Every country of the world has a Bill of Rights.

Following are the features of India Secularism:
- There is no such religious community which dominates the other or is superior to other community.
- The State is not allowed to enforce any particular religion on people nor take away their existing religion or freedom from the individuals.