Todd Toddler falls into Harambe-the-Gorilla's exhibit at the zoo. Samantha Samaritan leaps over the fence and rescues him. Todd's mother is so grateful she promises Samantha $1,000 for life. Samantha graciously accepts. Ms. Toddler's promise is

a.

Enforceable because of an unforeseen difficulty.

b.

Enforceable because a promise is always enforceable in court.

c.

Unenforceable because past consideration is no consideration.

d.

Unenforceable because it is knowable that Gorillas are dangerous.