— Why didn’t you come to play football with us yesterday afternoon?

— I ________ my mother with the housework then.

A．was helping

B．helped

C．had helped

D．have been helping

对于学生信息表：student(sno，sname，sex，age，dept)，如果把学生“张明”的姓名改为“张岩”，则正确的语句是

A．UPDATE SET sname＝‘张明’WHERE sname＝‘张岩’

B．UPDATE student SET sname＝‘张明’WHERE sname＝‘张岩’

C．UPDATE student SET sname＝‘张岩’

D．UPDATE student SET sname＝‘张岩’WHERE sname＝‘张明’