Which of the following is not a requirement of a practical fuel? a. it must occur in abundance in nature or be easy to produce. b. it must be made up of elements that combine easily with oxygen. c. it must contain a large amount of stored energy. d. it must be in the solid state to be used.

Option D: It must be in the solid state to be used.

A material that is used to provide energy is for work is known as fuel. For practical use, it is important that the fuel must occur in abundance or can be easily produced. It should be made of elements that can easily combine with oxygen. This is required for burning. It must produce large amount of energy. So, it must contain large amount of stored energy. It is useful only when a small quantity can produce large amount of energy. It can be in any state, solid liquid or gas.

Therefore, it is not important that it must be in the solid state to be used.

explanation:

a fuel engine ( known as a gasoline engine in american english )is an internal combustion engine with spark ignition, designed to run on petrol (gasoline) and similar volatile fuels.

object 2 because all the other ones are wrong