The hormone that increases the flexibility of the pubic symphysis during pregnancy is:
a. lh
b. hpl
c. cortisol
d. hcg
e. relaxin

The correct answer is option E. relaxin.

Explanation:

The relaxin hormone is produced and released by the placenta and ovary that cause important effects during pregnancy and the female reproductive system. This hormone increases the flexibility of the pubic symphysis during pregnancy.

Relaxin helps in relaxing the pelvic ligaments and softening and ripening of the cervix.  It helps in the softening of the cervix and vagina to aids the process of delivery.

Thus, the correct answer is option E. relaxin