The nuclear force is a short range force, this can be explained by fact that the binding energy per nucleon versus mass number curve

is flat for mass numbers in the range from 30 to 170. has a maxima for mass number 56 rises sharply with increase in mass number. falls for heavier masses

is flat for mass numbers in the range from 30 to 170.

The correct answer is Option (1) → is flat for mass numbers in the range from 30 to 170.