A hollow metal sphere has inner radius a and outer radius b. The hollow sphere has charge 2 Q. A point charge Q sits at the center of the hollow sphere. You may want to review (Page 658) . For help with math skills, you may want to review:

i am pretty sure it is c because when people are closer together, they cannot move as freely. picture being in a mostly full elevator, for instance. the people are right next to you, and you can barely move.

when two balls of the different masses are dropped from equal height, they reach the ground at the same time .this is because they experience the same acceleration.

the acceleration is independent of mass.

thus when they are dropped they will always maintain the same velocity and travel the same distance (neglect air resistance of course) at the same time.