Which force?

Friction, air resistance, tension, spring force, normal force, etc. are all due to

1. Gravitational interaction
2. Electromagnetic interaction
3. Strong interaction
4. Weak interaction

Ans. A. An electromagentic interaction refers to the interaction of two electrically charged objects by exchanging photons.

The force is everywhere

When two objects exchange forces, they can do so without having to contact each other.

1. Yes
2. No

Ans. What do you mean by contact? Does exchanging photons/gravitons count as contact? On a more practical level, it is very helpful to remember, "no contact, no force except gravity," in most problems of classical mechanics.

The work energy “theorem”

The work energy theorem, $\Delta T = W$ where $T$ is the kinetic energy (and $\Delta T = T_2 - T_1$ is its change) and $W$ is the net work done on the particle, is

1. always valid (in classical mechanics).
2. valid only for conservative forces.