Assertion : the binding energy per nucleon is practically independent of the atomic number for nuclei of mass number in the range 30 to 170 .
reason : nuclear force is short ranged.

A. both Assertion & Reason are True & the Reason is a correct explanation of the Assertion.
B. both Assertion & Reason are True but Reason is not a correct explanation of the Assertion.
C. Assertion is True but the Reason is False.
D. both Assertion & Reason are false.