5. 猪肉的价格已经上涨了，但是我不知道是否会保持下去。

(go up; remain)

4. 这位美国学生教我学英语来交换学汉语。(in exchange for)

3. 在动物园里，孩子们不允许接近那些看似安全的动物。(approach)

2. 这是我第三次告诉你不要把手机带到课堂上来。

(This/It is the third time that ...)

1. 到现在为止我们已经开办了两家新的医院。(up to now)

5. With the help of high technology, more and more new substances 　　　(discover) in the past years.

4. This is the third time I 　　　(visit) Hong Kong. The second time I 　　　(come) here was on Christmas Day last year.

3. It 　　　(be) six years since they 　　　(get) married.

2. I 　　　(receive) no reply from her so far.

1. You don’t need to describe her. I 　　　(meet) her several times.