[单选题]在Oracle中,有一个教师表teacher的结构如下:
ID NUMBER(5),NAME VARCHAR2(25),EMAIL VARCHAR2(50)
下面( )语句显示没有Email地址的教师姓名。 A.select name from teacher where email=null; B.select name from teacher where email<>null; C.select name from teacher where email is null; D.select name from teacher where email is not null;