It wasn't Mark that you met in the shop. (HAVE) It ____________ Mark that you met in the shop.
COULDN'T HAVE BEEN | COULD NOT HAVE BEEN | CAN'T HAVE BEEN
She was just going to have her breakfast when the phone rang. (ABOUT) She was just ____________ breakfast when the phone rang.
ABOUT TO HAVE HER
Steve didn't manage to complete his work. (FAILED) Steve __________ his work.
FAILED TO COMPLETE