Identify the correct overall shape of the average binding-energy-per-nucleon curve when the mass number A increases from 1 to about 250.
(a) It rises gradually, reaching a maximum near A≈238, and then falls slightly for the heaviest nuclei.
(b) It rises rapidly for very light nuclei, reaches a pronounced maximum near A≈56, and then falls gradually for heavier nuclei.
(c) It decreases steadily from the lightest to the heaviest nuclei without any maximum.
(d) It falls for light nuclei, touches a minimum near A≈56, and then rises sharply for heavy nuclei.