Which of these promises would be enforceable as supported by valid consideration?

Which of these promises would be enforceable as supported by valid consideration?

options:

1)   Your promise not to break any state or federal laws before you are 30.

2)   My promise to give you an A on the final in consideration of your past hard work.

3)   Your rich aunt's promise to change her will and leave you a fortune.

4)   Your promise to pay money in exchange for a promise to provide goods.