Which choice can be classified as a pure substance? salt water
Iced Tea
pumpkin pie
salt

Salt

Explanation:

It is because it has a defined composition.

Salt

Explanation:

Pure substances are those that contain atoms or molecules of the same type. For eg: elements are pure (gold, hydrogen etcl.) and compounds (such as water, sodium chloride, etc.), etc.

Rest of choice are impure because they contain a mixture of different things, like pie has eggs, or all sorts of other molecules, salt water has water and salt molecules, and iced tea has water and other molecules associated with tea.

the answer is d.) potassium