While other scientists are keeping__ __eye on changes in the H5N1 bird flu strain, the scientists in England are working on vaccines, in case it becomes highly infectious in __ __humans.
| A．a , / | B．an, / | C．the, an | D．an, the |
18. It was because of English girlfriend, believe it or not, ______ his English improved so greatly.
| A．which | B．as | C．that | D．what |
It was lack of money, not of effort, _____ defeated their plan.
| A．which | B．as | C．that | D．what |
I don’t know _____makes her afraid of having her business discussed.
| A．what it is about Mary that | B．that is it abut Mary what |
| C．what is it about Mary that | D．that is about Mary what |
15. It was with great joy _____ he received the news ______ his lost daughter had been found.
| A．because, when | B．which, that |
| C．since, how | D．that, that |
It was _____back home after the experiments.
| A．not until midnight did he go | B．until midnight that he didn’t go |
| C．not until midnight that he went | D．until midnight when he didn’t go |