Compared to a European option, the value of an otherwise identical American option is...(please explain)

a. sometimes less, and never greater.

b. always equal to the value of the European option.

c. sometimes greater, and never less.

d. always greater.

e. always less.

It is never rational to exercise an American ____ option on a ___________ stock prior to its expiration date.(please explain)

a. call ... dividend-paying

b. put ... non-dividend-paying

c. call ... non-dividend-paying

d. put ... dividend-paying