Final answer:
The type of fuel with a definite size and shape is a solid. Solids maintain a defined shape and volume because their particles are closely packed and vibrate around fixed points. Characteristics such as strong intermolecular forces and high melting points are indicative of a solid substance. Thus, the correct answer is option a.
Step-by-step explanation:
The type of fuel that has a definite size and shape is a solid. Solids are one of the three common states or phases of matter, the others being liquids and gases. The characteristic that distinguishes solids is that they maintain a defined shape and volume. The particles in a solid are packed closely together and vibrate around fixed axes, which gives the solid its definite shape and volume.
By contrast, liquids have a fixed volume but not a definite shape; they take on the shape of their container. Gases have neither a definite shape nor a definite volume as they expand to completely fill their container. Fossil fuels also come in all three states: coal is a solid, petroleum is a liquid, and natural gas is a gas.
To address, if a substance has strong intermolecular forces, a high melting point, and is not easily compressed, the substance is most likely a solid. This is because these characteristics are typical of solids due to the strong interactions between the particles making up the solid.