Final answer:
A solid state of matter has a definite shape because its particles are in a fixed position with regard to each other, unlike liquids and gases which do not maintain a rigid form. Option A is correct.
Step-by-step explanation:
Definite shape is a characteristic of a solid state of matter. When looking at the three states of matter—solid, liquid, and gas—solids have the unique property of maintaining a definite shape and volume. In a solid, the individual particles (atoms or molecules) are in a fixed position with regard to each other, and this arrangement gives solids their firm shape.
On the other hand, liquids have a definite volume but will take the shape of their container, and gases have neither a definite shape nor a definite volume. In contrast to solids, gas particles are far apart from each other in space, which allows them to completely fill their containers. Knowing these properties helps explain why answer a. solid is correct for the question about which state of matter has a definite shape.
The characteristic of having a definite shape is specific to solids. Solids have particles that are arranged in a fixed position with regard to each other. This arrangement gives solids a distinct shape that is retained even when external forces are applied to them.