在Oracle中,有一个教师表teacher的结构如下:IDNUMBER(5)NAMEVARCHAR2(25)EMAILVARCHAR2(50)下面哪个语句显示没有Email地址的教师姓名()
A.SELECTnameFROMteacherWHEREemail=NULL;
B.SELECTnameFROMteacherWHEREemail<>NULL;
C.SELECTnameFROMteacherWHEREemailISNULL;
D.SELECTnameFROMteacherWHEREemailISNOTNULL;