The gand education is the key to _____ ruralproblems.

Is there any flight to New York?— I think there ______ be, for it is snowing so heavily.

I can’t find my scissors , can you help me buy______ —Ok

Mr. Fox fell ill, thus __________ it necessary for us to find another person for his job.

观察下面4个选项,从中选出不同类的选项。