Good health is __________ most people take for granted--- until they lose it .

The chairman thought ___ necessary to invite Professor Smith to speak at the meeting . 

---Mum, have you seen my U-Disk? ---____________ you bought last Sunday? I'm afraid I haven't seen ________.

—Is there any mail?—No, ______ at all．

I dislike _____ when you speak loudly in public.