scientists have done a lot of research on A (H1N1) flu, there are still some cases for further study.[ ]

Why are you so late?—I was in half the way when it______to me that I had left my notebook home，so I had to fetch it.

Since you are in trouble, why not ______ our offer of help?

The weather in Guangzhou is hotter than ________ in Beijing in summer.

I’m sorry you’ve missed the train. It ten minutes ago.