Liquid ammonia is used for refrigeration because

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:

The property of hydrogen which distinguishes it from other alkali metals is

Deuterium differs from hydrogen in

When steam is passed over red hot iron,the substances formed are

In the reaction $2X + B_2H_6 \rightarrow [BH_2(X)_2]^+ [BH_4]^-$,the amine$(s)$ $X$ is(are):