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 |
We cannot figure out ________ quite a number of insects, birds, and animals are dying out.
| A．that | B．as | C．why | D．When |
Along with the letter was his promise ________ he would visit me this coming Christmas.
| A．which | B．that | C．what | D．whether |
The other day, my brother drove his car down the street at ________ I thought was a dangerous speed.
| A．as | B．which | C．what | D．That |
May and susan are twins and I can’t tell_____is_____.
| A．which ;who | B．which ;which | C．who ;whom | D．whom ;who |
Out of the airport ,my friend drove his car into the innermost lane,_____ had a sign “carpool only”.
| A．which | B．where | C．that | D．what |