---I wonder what makes you a good salesperson
---I _______ as a waiter for three years , which contributes a lot to my today’s work.
A. serve B. have served
C had served D. served
--- Don’t waste any paper, because our forests ____ every day.
----Sorry, I didn’t know that.
| A．decreased | B．had decreased | C．have decreased | D．are decreasing |
. The child, who 
has a gift for sports, might make a first-class tennis player if given chances to develop her ______.
| A．courage | B．habit | C．potential | D．sense |
---Did Jack come back early last night?
---Yes, it was at eight o’clock_____ he arrived home.
| A．before | B．when | C．that | D．until |
If you insist on driving like this, you will have to suffer the ____ sooner or later.
| A．causes | B．consequences | C．exchanges | D．achievements |
He did well in the examination. He _____ hard at his lessons..
| A．must have worked | B．can have worked |
| C．will have worked | D．has worked |