When I was at school, I _____ up very late, reading storybooks.
| A．used to stay | B．was used to stay |
| C．used to staying | D．am used to staying |
No matter how bright a talker you are, there are times when it's better __________ silent.
| A．remain | B．be remaining |
| C．having remained | D．to remain |
I remembered __________ the door before I left the office, but forgot to turn off the lights.
| A．locking | B．to lock |
| C．having locked | D．to have locked |
George returned after the war, only __________ that his wife had left him.
| A．to be told | B．telling |
| C．being told | D．told |
Having finished her project, she was invited by the school __________ to the new students.
| A．speaking | B．having spoken |
| C．to speak | D．to have spoken |
Let those in need __________ that we will go all out to help them.
| A．to understand | B．understand |
| C．understanding | D．understood |