Which set of elements forms stable,covalent,and hydrogen-bonded hydrides?

Calcium imide on hydrolysis gives gas $(B)$ which on oxidation by bleaching powder gives gas $(C)$. Gas $(C)$ on reaction with magnesium gives compound $(D)$ which on hydrolysis again gives gas $(B)$. Identify $(B)$,$(C)$ and $(D)$.

The calorific value of producer gas is low because of:

Isotope$(s)$ of hydrogen which emits low energy $\beta^{-}$ particle with $t_{1/2}$ value $> 12 \ years$ is/are :

The synonym for water gas when used in the production of methanol is:

Which of the following is not an isotope of hydrogen?