Question

which is correct for action and reaction
A.act on different body
b.have resultant zero

Answer 1

I think that the options are correct

Answer 2

I do not really understand your question, but I hope this helps.
When you add the two force and reaction force vectors, you get zero. That is because the action and reaction forces are equal in magnitude and opposite in direction.
In this picture-if you can see it-in the first case there is an action and reaction pair, but the reation force is not necessarily acting on a body. Same for the fist pair of the second part of the diagram, but for the second pair, both forces act on a body.
Hope this helps!
--Diana