Though the novel had a happy ending, the readers were left ____.
26.Even if there is no scientific proof yet ______ secondhand smoke causes cancer, there is no reason why nonsmokers should be forced to take this risk.
25.With so little time ______ on math, it is all too easy for children to ignore practicing mathematics, which is a kind of language.
24.One recent prediction is that within the next 50 years, it ______ possible to link the human brain directly with a computer.
23.—I have ______ high temperature and ______ sore throat. —Well, you may have the flu.
22.The site is fairly near the city center, ___ it can only be reached by a series of narrow streets.