He tried to avoid ______ my questions in class.
| A．to answer | B．answering |
| C．having answered | D．to have answered |
One can’t do extreme sports _________ he or she has had some training.
| A．if | B．unless | C．once | D．since |
--David, are you 1istening to me?
--Sorry, Dad. I _______ to make sense of what the reporter said.
| A．was trying | B．have tried | C．am trying | D．tried |
The road construction is based on the agreement, one of _______ purposes is to ensure its completion on time.
| A．which | B．whose | C．that | D．what |
Many approaches have been _______ to control the spread of H7N9 Bird Flu.
| A．adapted | B．employed | C．negotiated | D．accessed |
–Carla _______ go to that historical museum after school when she was a teenager.
--No wonder she is so familiar with it.
| A．could | B．should | C．might | D．would |