Read the passage and correct the mistakes, ______．
| A．if not | B．if any | C．if ever | D．if never |
At times, worrying is a normal, ________ response to a difficult event or situation --- a loved one being injured in an accident, for example.
| A．effective | B．individual | C．inevitable | D．unfavorable |
This cake is very sweet. You _____ a lot of sugar in it.
| A．should put | B．could have put | C．might put | D．must have put |
He paid for a seat, when he ______ have entered free.
| A．could | B．would | C．must | D．need |
— The woman biologist stayed in Africa studying wild animals for 13 years before she returned.
— Oh, dear ! She ______ a lot of difficulties !
| A．may go through | B．might go through |
| C．ought to have gone through | D．must have gone through |
Helen ______ go on the trip with us, but she isn’t quite sure yet.
| A．shall | B．must | C．may | D．can |