题目

 Li Ming, as well as his parents , ____ to the party.    A. has invited          B. was invited       C. have invited     D. were invited 答案：B称取铜、锌混合物粉末10.0g置于烧杯中，慢慢加入稀硫酸使其充分反应，直至固体质量不再减少为止，此时用去49.0g稀硫酸．剩余固体3.5g．（1）该混合物粉末中铜的质量分数为多少？（2）所用的稀硫酸溶质的质量分数是多少？