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

The gas which is present in both the natural gas and the bio-gas is

Of the options listed below, the speed of sound is highest in _____ at 25°C. 

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

Read the following questions carefully and answer them. 

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

Halogens are belonging to:

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

Solutions having the same osmotic pressure at a given temperature are called_____.