<u>D.</u>
For every action ther is an equal and opposite reaction.
equal in force, opposite in direction
Answer:
B) (-2.0 m, 0.0 m)
Explanation:
Given:
Mass of particle 1 is, 
Mass of particle 2 is, 
Position of center of mass is, 
Position of particle 1 is, 
Position of particle 2 is, 
We know that, the x-coordinate of center of mass of two particles is given as:

Plug in the values given.

We know that, the y-coordinate of center of mass of two particles is given as:

Plug in the values given.

Therefore, the position of particle 2 of mass 3.0 kg is (-2.0 m, 0.0 m).
So, option (B) is correct.
<h2>
After 1 hour they meet.</h2>
Explanation:
Distance between them = 6 miles
Speed of uphill person = 2.5 miles per hour
Speed of downhill person = 3.5 miles per hour
Relative velocity = 2.5 - ( -3.5 ) = 6 miles per hour
We know
Displacement = Velocity x Time
6 = 6 x Time taken
Time taken = 1 hour
After 1 hour they meet.
Im not sure but it might be the last option: it gives reasons to be believed and trusted