The split between humans and living apes is thought by some scholars ____ 15 to 20 million years ago.
| A．to occur | B．occurring | C．to have occurred | D．having occurred |
We agreed to accepted ______ they thought was the best tourist guide.
| A．whatever | B．anyone | C．whichever | D．Whoever |
You may______remember some idioms in the texts but you couldn’t ______ remember all the words in them.
| A．probably; possibly | B．possibly; likely |
| C．probably; likely | D．likely; possibly |
Why! I have nothing to confess. ______ you want me to say?
| A．What is it that | B．What it is that |
| C．How is it that | D．How it is that |
The best method to ______ this goal is to unite as many people as possible.
| A．undertake | B．conduct | C．perform | D．Accomplish |
Scientists say it may be five or six years _____ it is possible to test this medicine on human patients.
| A．since | B．after | C．before | D．When |