题目

The number of the students in our grade _______about ______，and of them are girls. A . are, six hundreds, two- thirds B . is, six hundred, two- third C . is, six hundred, two thirds D . are, six hundreds, two third 答案：C12．有大、中、小球共232个，价值1000元，其中小球的数量是中球的4倍，大、中、小球单价分别是21元、9元、2元，那么大球有多少个？（用方程组）