MySQL中，查询created_time在2022年之前的记录，以下查询效率最低的是（）？
CREATE TABLE `student_table` (
`id` bigint NOT NULL AUTO_INCREMENT,
`name` char(10) DEFAULT NULL,
`created_time` datetime DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `index_created_time` (`created_time`)
) ENGINE=InnoDB
A.
SELECT * FROM student_table WHERE created_time < '2022-01-01' ;
B.
SELECT * FROM student_table WHERE created_time <= '2021-12-31' ;
C.
SELECT * FROM student_table WHERE substr(created_time,1,10) < '2022';
D.
SELECT * FROM student_table WHERE created_time < '2022-01-01 00:00:00' ;
E.
SELECT * FROM student_table WHERE created_time < substr('2020-02-11 22:06:17',1,10);
