When I called you this morning, nobody answered the phone. Where __________?
| A．did you go | B．have you gone |
| C．were you | D．had you been |
Claire thought it was ridiculous sympathy by a robot.
| A．to offer | B．to be offered | C．to be offering | D．to have offered |
There is no doubt the earth is becoming warmer.
| A．whether | B．that | C．if | D．why |
Using a telescope we could see that something .
| A．is happening | B．happened | C．would happen | D．was happening |
all day, I went to bed early.
| A．Working hard | B．Worked hard | C．Having worked hard | D．To work hard |
There is a natural phenomenon scientists call the greenhouse effect.
| A．that | B．what | C．for which | D．who |