用户表 user 中存在一个字段 age ,下面那个 sql 语句表示 " 查询年龄为 18 或 20 的用户 "
A.
select * from user where age = 18 or age = 20;
B.
select * from user where age = 18 && age= 20;
C.
select * from user where age = 18 and age = 20;
D.
select * from user where age = (18,20);