Mr. Xue enjoyed ________ by working in Yangzhou-Taizhou Airport because he always hates ________ while staying alone at home all day long.

One of the most important questions they had to consider was ______ of public health.

With children, if you say "no", you have to mean ______.

----Have you seen Tom and Mary?----I haven’t seen____ of them. 

I have _____________ to tell you.