If you are looking for a sentence in that paragraph to support the main idea, I think it would be "All it requires is a good pair of sneakers-no cables, stylish outfits, or weights required. The main idea is basically that walking is a good and easy way to begin exercising, and that explains it.
D) There is no way to tell if he is less-qualified.
Hope this helps, baiii<3
Im guessing its B, Because it just makes more sense! I went in there and read it aloud using both words (A and B) B made more sense. With an object being measured, such as a lemon, to make a quart of lemon juice, Id say you'd use the word number. Amount is not a word used for an object or measurement.
A ghost delivers a supernatural kiss of death