There are several possibilities. Here are a few that occur to me:
-- If Point-A is the summit of Pike's Peak, he may feel somewhat
short of breath.
-- If Point-A is his grandmother's house, he may feel a great sense
of pleasant anticipation.
-- If Point-A is his office on Monday morning, then he may feel
a tightening sensation in his chest.;
-- If Point-A is his home on Friday afternoon, then he feels the
effects of a slow and steady drop in his blood pressure.
I finer point might be put to it if we had any idea of where
Point-A is, and what it represents in the grand scheme
of things.
Answer: A, B, and D,
C is incorrect because continental drift takes several centuries to move the tectonic plates witch is not an immediate impact leaving you with A,B, and D.
Answer:
Gravitational
Tension
Normal
Friction.
Explanation:
The forces acting on the sled are:
Tension: the tension from the rope, this is the force that "moves" the sled.
Friction: kinetic friction between the sled and the ground as the sled moves.
There are another two forces that also act on the sled, but that "has no effect"
Gravitational force: This force pulls the sled down, against the floor.
Normal force: This force "opposes" to the gravitational one, so they cancel each other.
These two forces cancel each other, so they have no direct impact on the movement of the sled. BUT, the friction force depends on the weight of the moving object, and the weight of the moving object depends on the gravitational force, so we need gravitational force in order to have friction force.
Then we can conclude that the forces acting on the sled are:
Gravitational
Tension
Normal
Friction.
Explanation:
We have,
Surface area, 
The current varies wrt time t as :
(a) At t = 2 seconds, electrical charge is given by :
(b) Current is given by :
Instantaneous current at t = 1 s is,
(c) Current is, 
Current density is given by electric current per unit area.
Therefore, it is the required explanation.
