Newton's law of universal gravitation is an INVERSE SQUARE LAW, which rules out C and D.It is proportional to the masses involved, which rules out B.A could be seen as one form of the lawF=G m1 m1/r^2Though I recognise it more as F=G m1 m2/r^2.G is the universal gravity constant and is distinct from g which is the acceleration of gravity LOCAL to a planet or moon. So, g is LOCAL, G is universal.Newton was a smart bloke, as are all these scientists whose names frequently appear.