When acceleration is held constant and objects of different mass are observed, are mass and force directly proportional or inversely proportional? explain.

Yes. When two things are directly prortional, that means that as one increases, the other increases at the same rate. So, say you have a 2kg object at an acceleration of 2m/s^2. The force would be 4N. If you have a 3kg object at an acceleration of 2m/s^2, the force would be 6N. If two things are inversely proportional, that means that as one thing increases the other decreases at the same rate. A good example of this is in a chemical reaction. If you increase the surface area of the reactants, the reaction time decreases. They are inversely proportional.

Ithink 2 is the correct

The answers are 3.c kelvin4.b liquids only