Which sentence needs proofreading? A) Jenny turned around quickly when she heard all the books on the top shelf fall down suddenly. B) Having made sure that all the doors and windows in the old house were locked and unable to be opened. C) Heather hung her head down and began to cry a little when she only received the First-Runner-Up ribbon. D) "Before you leave the house today," said Mrs. Miniver, "you need to make sure that all the beds are made."