The correct option is
A Gravitational
The universal gravitational constant is of the order
6.67384×10−11 m
3 kg
−1 s
−2 making it the weakest forces compared to the rest. Gravitation range to infinity. However, it is the weakest of the fundamental forces. The gravitational strength is only
6×1039 of the strength of the strongest nuclear force.
Electromagnetic force: The relative strength of the electromagnetic force is 1137 of the strong nuclear force. Its force drops off as the square of the separation between charged particles or magnetic poles, although the range is infinite.
Nuclear force: The relative strength of the strong force is designated as 1. The range of this force is small, approximately 1015 m. Apparently, this force does not decrease by the inverse square as do the gravitational and electromagnetic forces. Instead, it just stops at its given separation.
Electrostatic force: Electrostatic force is not a natural occurring force. The weak form of electrostatic force can be generated by rubbing ebonite with flannel. Even though electrostaticaly induced forces seem to be rather weak, the electrostatic force between an electron and a proton, that together make up a hydrogen atom, is about 36 orders of magnitude stronger than the gravitational force acting between them.
From the above discussion, it is clear that gravitational force is the weakest.