251.（10-11，辽宁省大连市二十三中高二上期中）---Chinese has a large vocabulary, hasn’t it?.
----Yes. _________more words and expressions and you will find it easier to read and communicate.
A. Mastering B. To master C. Master D. Having mastered
252.（10-11，四川省成都市七校协作体高二上期中）In order to make our city green, .
A. it is necessary to have planted more trees B. many more trees need to plant
C. our city needs more trees D. we must plant more trees
