Both elements and compounds have fixed composition and a definite set of properties.

The correct option is A True

Pure Substance:

• Any substance that is made up of a single type of particles that have a definite set of properties and the same chemical nature is called a pure substance.
• It contains only one kind of particle. It can be an element or a compound.
• For example water, sugar, salt, sodium, tin, etc.
• i) Elements - examples are iron, silver, gold mercury, etc.
• ii) Compounds - examples are water, carbon dioxide, methane, vinegar, etc.

Thus, the given statement is True. I.e., Both elements and compounds have fixed composition and a definite set of properties.