171.In China, all the students work hard at school _____ going to university for higher education in the future.

A. in the habit of
B. in the hope of
C. in search of
D. in honor of

172.Mary dropped in _____ Mr. Smith, but he wasn't at home, so she went to drop in _____ Mr. Smith's office.

A.on；on
B.at; at
C.on；at
D.at；On

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