Answer:
Option A is the correct answer.
Explanation:
The main ideas refer to the most important idea in a text; they are used to build the text around them with supporting ideas. In this case, the main idea is walking is not the most exciting form of exercise a person can take on for fitness. It is <u>explicit because it is directly stated in the paragraph</u>. Supporting ideas such as the description as a "simple activity" or the few things needed for this.
