He will _____ our class to sing at the school singing contest. A. take place of B. stand for C. represent D. representative of 答案:C 解析: take place of 短语不完整,take the place of意思是“代替…位置”; represent“作为…的代表”; stand for“作为…的标志、符号等”。将适量的下列物质溶解于水的过程中,会使溶液的温度显著降低的是 ( ) A.浓硫酸 B.硝酸铵 C.火碱 D.蔗糖