It is fairly common in Africa for _______ a group of musicians surrounded by others who also join in the performances. A. there are B. there being C. there to be D. there be 答案:C 考查there be句型动词不定式的复合结构形式。此处it是形式主语,介词for后应用there to be结构,故选C。 若用乙烯和氯气在适当的条件下反应制取六氯乙烷,这一过程中所要经历的反应及耗用氯气的总的物质的量是(设乙烯为1 mol,反应产物中的有机物只是六氯乙烷)?? ( )。A.取代,4 mol Cl2B.加成,2 mol Cl2C.加成、取代,3 mol Cl2D.加成、取代,5 mol Cl2