He started to work dilligently _____ he came up with the idea of hybrid rice for the first time in the 1960’s.
| A．at once | B．the moment | C．for the moment | D．in no time |
Listen! Do you hear someone for help?
| A．calling | B．call | C．to call | D．called |
It rained heavily in the south，_______ serious flooding in several provinces.
| A．caused | B．having caused | C．causing | D．to cause |
Mrs. White showed her students some old maps ______ from the library.
| A．to borrow | B．to be borrowed | C．borrowed | D．borrowing |
Mark ______ have hurried. After driving at top speed, he arrived half an hour early.
| A．needn’t | B．wouldn’t | C．mustn’t | D．couldn’t |
People have always been ______ about exactly how life on earth began.
| A．curious | B．excited | C．anxious | D．careful |