David had prepared carefully for the chemistry exam, as he wanted to be sure of passing it at the first _____.

--I hear that the famous singer Eason Chan will sing at Beijing New Theatre.--Really? Where did you _____? 

To avoid           on how to use the word, you’d better refer to a dictionary.

The Sanlu Milk Powder event is a clear indication that food safety is a big problem; nobody can __   _ all foods are secure to us, but we are sure that the situation is turning for the better.

You have nothing to___ by refusing to listen to our advice.