请教几道英语翻译

1.他当过总统助理。 （assistant)

2.实际上，你有义务把董事会（the board)的决定通知他。 （inform sb of sth)

3.她关上了窗户不让蚊子进来。 （so as to）

4.只有这样，才能解决问题。 （“only+介词短语”位于句首）

5.我能想起很多这样的例子：学生们很明显（obviously）知道很多英语单词和表达，但是写不出一篇好文章。 （cases+where引导的定语从句）

He worked as assistant to the president

In fact, you are obliged to inform him the board's decision

She closed the windows so as to prevent mosquitoes coming

Only in this way can we solve this problem

I can think of many such examples: the students were obviously aware that many English words and expressions, but could not write a good article