_____ he met with the difficulty did he realize the importance of group work.
| A．Even though | B．Never until | C．Only before | D．Ever since |
"On no account ____to feed the animals", the warning can be seen on the signboard in front of every cage.
| A．allow visitors | B．visitors are allowed |
| C．are visitors allowed | D．are allowed visitors |
Thinking ______ you know_______ in fact you don’t is a terrible mistake.
| A．that; that | B．what; what | C．that; what | D．what that |
He is only too ready to help others, seldom, ____, refusing them when they turn to him.
| A．if never | B．if ever | C．if not | D．if any |
--- Don't worry. I've just sent an ambulance to you. They ________ be there any second.
| A．could | B．might | C．would | D．should |
At first he was not satisfied with the new job but decided to give himself a few months to see ___________ it got any better.
| A．when | B．how | C．why | D．whether |