Mary liked to look back on her high—school days， she thought were the happiest in her life．
| A．that | B．what | C．which | D．when |
We often talk a great deal about English language teaching, ______ that it is the learning that really matters.
| A．having forgotten | B．forgotten | C．forgetting | D．to have forgotten |
Many companies give away small quantities of their produce as samples ______ people can try them before buying them.
| A．if | B．because | C．so that | D．since |
In the rainforest of the Amazon, 50 to 150 plant species ______ every day.
| A．are being destroyed | B．are destroying |
| C．have been destroyed | D．destroyed |
— This is a good place for a picnic.
— Yes, it couldn't be ____ .
| A．better | B．best | C．worse | D．worst |
He was very busy yesterday, otherwise he ____ to the meeting.
| A．would come | B．would have come | C．came | D．had come |