What should come in place of the question mark (?) in

Which one of the following gases is supporter of combustion?

A day is considered a rainy day when it receives a rainfall of:

What do we call sound waves with frequencies below 20 Hz?

Tear gas used by the police to disperse the mob contains –

Which of the following element is found in maximum percentage in the human body?

What is the percentage of nitrogen present in farm yard manure (FYM) in general?

In circular motion the direction of velocity changes at _______ points.

Iron sheet kept in moist air covered with rust. Rust is 

What type of immunity is provided by vaccination?

Which subatomic particle has negligible mass ?