B. a covalent bond because a covalent bond is when 2 atoms share either 1 or more than 1 pairs of electrons, and valence electrons are the type of electrons that are shared in a covalent bond.
Average velocity is the ratio of the total distance travelled to the total time spent.
Instantaneous velocity is the average velocity a body as the time tends to zero
So I’m gonna answer the first question on the second page:
For P the force is friction and for Q the force is forward thrust resultant force
Yes. 'Equilibrium' means that the SUM of adding up all the forces acting on the object is ZERO.
If you add up all the forces acting on the object and the sum is NOT zero, then the object is NOT in equilibrium. The force you have to add to it is whatever it takes to cancel out (balance) all the forces that are there now.
Take the SUM you got when you added up all the existing forces. To get equilibrium, ADD ON one new force with the SAME magnitude, in exactly the OPPOSITE direction.