由表1可知，该厂销售额中，销售成本占销售收入的（）
A．2/3
B．1/3
C．1/4
D．1/2
参考答案：A
—Any information about your son?
—No. If only I ______ those tough words to him.
A．didn't say
B．hadn't said
C．shouldn't have said
D．couldn't have said
分泌胆囊收缩素的是（）
A．主细胞
B．壁细胞
C．颈黏液细胞
D．G细胞
E．Ⅰ细胞
