Question

notion means : a vague idea in which some confidence is placed a quantity that does not vary an inquiry into unfamiliar or questionable activities the testing of an idea

Explanation:

The word "notion" commonly refers to a vague idea in which some confidence is placed. The other options describe different concepts. A quantity that does not vary is a constant. An inquiry into unfamiliar or questionable activities is an investigation. The testing of an idea is experimentation.

Answer:

A. a vague idea in which some confidence is placed