Which of the following acids does not produce $H_2$ gas upon reaction with alkali metals?

Which one of the following substances is used in the laboratory for a fast drying of neutral gases?

$NaH$ is an example of:

Given below are two statements :
Statement-$I$: Methane and steam passed over a heated $Ni$ catalyst produces hydrogen gas.
Statement-$II$: Sodium nitrite reacts with $NH_4Cl$ to give $H_2O$,$N_2$ and $NaCl$.
In the light of the above statements,choose the most appropriate answer from the options given below :

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A:$ Hydrogen is an environment-friendly fuel.
Reason $R:$ Atomic number of hydrogen is $1$ and it is a very light element.
In the light of the above statements,choose the correct answer from the options given below:

Hydrogen has three isotopes. The number of possible diatomic molecules will be: