Which condition involves the tightness of the foreskin that prevents it from being pulled back?

Phimosis is the correct answer because it specifically refers to the condition where the foreskin cannot be retracted over the glans (head) of the penis due to tightness. This is often a normal condition in infants and young boys, but if it persists, it may lead to complications such as infections or discomfort, prompting medical evaluation or treatment.

The other conditions listed have different meanings: castration refers to the removal of the testicles; epispadias is a congenital condition where the urethra does not develop properly, leading to its opening on the upper side of the penis; and cryptorchidism is the condition where one or both testicles have not descended into the scrotum. These definitions highlight how phimosis is uniquely characterized by the tight foreskin issue, making it the accurate choice.