Please explain why those of the options are not enforceable contracts.

Which of the following would most likely be a valid enforceable contract: a. Scion and Finlay agree that Scion will sell his green 200? Mazda motor vehicle to Finlay. Scion is 16 years old. b. Scion and Finlay agree that Scion will give his green 200? Mazda motor vehicle to Finlay. c. Scion and Finlay are negotiating for the purchase of his car. Finlay says \"sell me the car for $2,000 or I will blow up your house." Scion agrees and they enter into a written contract. d. Scion and Finlay are negotiating for the purchase of his car. Finlay was in a horrible accident several years prior and is 100% blind. The parties agree to a price of $4,000. The parties sign a written agreement memorializing their agreement. e. Scion and Finlay enter into a contract to \"buy Scion's really cool car for $4,000.\" Scion owns two motor vehicles. Finlay thinks he is buying Scion's really cool Mazda. Scion thinks he is selling his really cool BMW. f. None of the above contracts would be enforceable