please answer asap

Which XXX function removes the map entry John from the guest list? int main () \{ map guestIn; guestIn. emplace ("Bob", 1); guestIn. emplace ("Bill", 2); guestIn.emplace ("Mike", 3); guestIn. emplace ("John", 4); XXX \} a. guestln.erase("John"); b. guestln.clear("John"); c. guestln.at("John"); d. guestln.pop("John")