Compare LPG and wood as fuels.

Compare and contrast fossil fuels and the sun as direct sources of energy.

Compare and contrast nervous and hormonal mechanisms for control and coordination in animals.

What are the advantages of using CNG and LPG as fuels?

Compare and contrast biomass and hydroelectricity as sources of energy.

Compare and contrast the arrangement of elements in mendeleev's Periodic Table and Modern Periodic Table.

What is a good fuel?

Suggest two materials other than hydrogen that can be used as fuels in fuel cells.