The first question, uniform sliding means that friction is equal to thrust, then thrust is friction100 * 9.8 * 0.3 = 294 n.

The second question is simple: 20 * 9.8 =196n;

The third question, which is also very simple, is that gravity is 1/6 of the earth, so people with the same strength move things six times as hard as those on the earth, so the answer is C.