Mention the major cause of air pollution in metro cities. Write any three ways by which it can be reduced .

What are the major causes of water polluction ? Write any two causes only.

What is rancidity ? Mention any two ways by which rancidity can be prevented.

Explain any three major causes of biodiversity loss .

The major source of pollution upto 80% of total air pollution in metroplitan cities is

Mention any three characteristics of cancer cell. Mention its causes.

At an election , a voter may vote for any number of candidates , not greater than the number to be elected . There are 10 candidates and 4 are to be elected , If a voter votes for at least one candidates, then the number of ways in which he can vote is :

Carbon cannot be used to reduce the oxide of sodium, magnetsium, calcium, etc.to their respective metals. State the method used for obtaining these metals from their salts. For obtaining sodium from its compound. a. Name the salt used, gas produced, and the electrode at which the metal deposits. b. Show the chemical reaction taking place during the process. c. Name any two other metals which can be obtained from its compounds by the above method.

Five distinct letters are to be transmitted through a communication channel. A total number of 15 blanks is to be inserted between the two letters with at least three between every two. The number of ways in which this can be done is :