Select the correct answer from each drop-down menu.
Complete the following sentences about using biomass as an energy source.

While we can burn biomass to extract energy from it, its most significant use in transportation currently arises from xxxx .

A promising future application of biomass is xxxx .

Options for 1st section

-microbial action to produce hydrogen from it

-its conversion to liquid fuels

-microbial action to produce natural gas from it

Options for 2nd Section -

-to produce electricity in fuel cells

-as a natural coolant in cooling systems

-as a major source of hydrogen