Read the following questions carefully and answer them. 

The gas used for artificial fruit ripening of green fruit is —

In which state of matter, the distance between the molecules is minimum ?

Which of the following are metals found in free state in the earth's crust?

During uniform motion of an object along a straight line, its ___________ remains constant with time.

The coil in a heater is made of

Fe has 26 protons in its nucleus. What are the number of electrons in Fe²⁺ (II) ion?

A catalyst is a substance that_________ the velocity of a chemical reaction.

Which is the most economical method of removing solid matter from water?