1.Water in rural areas is disinfected by

2.Which of the following is the hardest metal ?

3.All the following noble gases are present in the atmosphere except

4.Equal volumes of all gases at the same temperature and pressure contain equal number of molecules. This law is called as

5.Given below are two statements, labelled as Assertion (A) and Reason (R). In the context of the two statements, which of the following is correct ?Assertion (A) : Moons gravity is one eighth of the earths gravity.Reason (R) : Due to less gravity moon is unable to retain its atmosphere.