Cars do cause us some health problems—in fact far more serious ________ than mobile phones do.

No progress was made in the trade talk as neither side would accept the conditions of      .

— May I have some more tea with sugar，please?—I'm sorry，but there doesn't seem to be________.

— Do you often talk with your friends on the telephone or mobile phone?  — __________ . I like using QQ. 

I will never know what was on his mind at the time, nor will _______.