The PTA is forming a subcommittee to purchase new equipment for the school's swim team. There are nine parents and twelve teachers who are available to join this 7-person subcommittee. In how many ways can the subcommittee be formed if there must be at least 1 parent on it? O A. 7 ) - ( 12 O B. 7 21 9 O c. 7 12 OD. 7 21 12 O E