Electronic devices such as iPods and headphones can do great harm to our hearing if _______ improperly.
| A．being used | B．used | C．to be used | D．having been used |
--Shall Mary come and play computer games?
--No,__________ she has finished her homework.
| A．when | B．if | C．unless | D．once |
--I'm sorry, I shouldn't have been so rude to you.
--You___________ your temper but that's OK.
| A．have lost | B．had lost | C．did lose | D．were losing |
Whether ways will be found to stop pollution or not is just___________ worries the public.
| A．why | B．which | C．that | D．what |
The plan __________just because people were unwilling to cooperate (合作).
| A．broke down | B．pulled down | C．turned down | D．put |
The customer bargained with the shopkeeper for a long time, and finally they agreed ___________ the price.
| A．to | B．with | C．on | D．at |