What is the average lifespan of a human red blood cell

Which one of the following is not a greenhouse gas? 

Which one of the following contributes largely to the greenhouse effect?

Find the odd one:

The chief source of naphthalene is 

The electronic configuration of an atom having atomic number 20 is 

When water itself combines chemically with some element or mineral it is called 

When Hydrogen starts burning in air it produces?

The most reactive among the halogens is 

Of the following which one pollutes the air of abig city? 

KMN04 can be used as a/an