The constancy of the binding energy in the range 30 < A < 170 in binding energy curve, is a consequence of the given fact:

Nuclear forces are short ranged

The correct answer is Option (2) → Nuclear forces are short ranged

The number force is short range force. It is clear from the fact that if distance between nucleons is more than few fermi then the binding energy (for a little large size nucleus becomes almost constant).

Thus beyond certain range force has no much influence.