We don't have to attend class for two days.

　　我們可以有兩天不用上課。

　　I have to work overtime today, so I can't attend class.

　　我今天得加班，不能來(lái)上課了。

　　What is the most convenient time for you to attend class?

　　您上課最方便的時(shí)間是什么？