A.For every action there is an equal and opposite reaction.
B. The greater the mass of an object, the more force is needed to cause the object to accelerate.
C. An object at rest or in motion will remain at rest or in motion unless acted upon by an unbalanced force.
D. When balanced forces act on an object, there is no change in the object's position.
The answer to this question is A. A simple Google search will help you find the answer. But, straightforward. That's what he stated in the document he made as the third law. So, that's the answer. Period.