Which pair of following forces will never gives resultant force 2Newton? A,2N and 2N B,1N and 1N C,1N and 3N D,1N and 4N N stands for Newton

No matter their directions, forces of 1N and 4N cannot add to 2N.
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When added graphically, two forces and their resultant form a triangle. Thus the triangle inequality applies. The magnitude of the resultant will never be larger than the sum nor smaller than the difference of the magnitudes of the component forces.

The sum of 1N and 4N forces will be between 3N and 5N. 2N is not in that range.