What ______ the doctors most was that they could not find the cause of the disease.

Mr. Smith has ___collection of coins than anyone else I have ever met.

(2009浙江宁波质检)Since David ________ downloaded a virus into his computer, he can not open the file now．

(湖南省雅礼中学2009届高三第七次月考 )—Are you pleased with what he has done?—It couldn’t be ________ . Why didn’t he put more effort into his work?

This is a(n) __________ arrangement,not a permanent one.