How is energy released from methane?

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

Combustion of octane takes place in an automobile engine.The homogeneous equation of combustion is :${\mathrm{C}}_8{\mathrm{H}}_{18}+\frac{25}{2}{\mathrm{O}}_2\to 8 {\mathrm{CO}}_2+9 {\mathrm{H}}_2\mathrm{O}$

the sign of $∆\mathrm{G}$ for the reaction will be :

Liquid ${\mathrm{H}}_2$ is used as rocket fuels.

Explain the following:

Liquid hydrogen cannot be used as a fuel easily.