Answer: The correct answer is silver.
Step-by-step explanation:
Matter that has a consistent and uniform composition—the same number and kind of atoms bound in the same way—is referred to as a substance. The substances are either elements or compounds. Only silver is a substance out of the alternatives offered because it is an element and all silver materials only contain silver atoms. In the same way that gasoline is a mixture of liquids whose composition can change, air is a mixture of different gases, and steel is an alloy (a mixture of compounds and elements) whose composition can change. Therefore the silver is the correct answer.