How long _______ in Shanghai?—I will be there attending a conference and giving a speech, which will take about 3 days

I’d like to buy some books by Mo Yan.—Sorry, they out just now .

I have bought two ball-pens, _______ writes well.

The collected money should be made good use __________the people who suffered a lot in the earthquake.

Not until the teacher explained theimportance of getting up early ______ we promise to come early.