1 . But spending too much time online is unhealthy and _________________ (使……很难集中精力于) on other things in life. (根据汉语提示完成句子)

2 . 人们一致认为环境污染已经成了最严重的问题之一。（recognize）
______ ______ ______ ______ environment pollution has become one of the most serious problems.

5 . The scenery in Guilin is believed to be the best in the world. (同义句改写)
It is __________ __________ the scenery in Guilin is the best in the world.

6 . My brother ________(觉得很难适应新的校园生活).(根据汉语提示完成句子)

8 . 令人惊喜的是，直到20世纪70年代，现代人才有人知道它们。
________________ no one in modern times knew about them until the 1970s.

9 . 我有点担心在高级课程中无法跟上其他学生，而且要适应所有的作业会相当困难。
I’m a bit worried about________ ________ ________the other students in my advanced course, and it’ll be quite difficult________ get used to all the homework.