Scientists say it may be five years ______ it is possible to test this medicine on human patients．
| A．since | B．until | C．before | D．when |
His face looks brown because he works ____ all day.
| A．indoor | B．outdoor | C． indoors | D．outdoors |
I'm not sure whether this is the room ________ she left her dictionary.
| A．where | B．that | C．which | D．in that |
---Don't put the waste on the ground.
---Oh, I'm very sorry. I ________ the dustbin（垃圾箱） there.
| A．don't see | B．isn't seeing | C．didn't see | D．haven't seen |
By the time she ________ home, her parents will have prepared some delicious food for her.
| A．will get | B．will have got | C．is getting | D．gets |
---Whose advice do you think I should take?
--- ________ .
| A．You speak | B．That's it | C．It's up to you | D．You got it |