Which of the following contracts might be specifically enforceable?

A has contracted to sell his house to B but has changed his mind and no longer wishes to sell it.

C has contracted to buy a new Ford motor car but the garage is now refusing to honor the contract.

D has contracted to purchase a number of tins of fruit for her business but the seller has now stated that he no longer wishes to proceed with the contract.

E has contracted to sing at a concert organized by F, but E has withdrawn as he has received a more lucrative offer from G.