单选题 The ratio of girls to boys in a class is 3 to 4. If there are a total of 28 students in the class, how many girls are there?
【正确答案】 A
【答案解析】班级里女生对男生的比例是3：4，那么女生在班级里所占的比例是3/7，3/7×28=12，所以选择A。