有如下存储过程: DELIMITER // CREATE PROCEDURE CountProc1(IN s_gender VARCHAR(50),OUT num INT) BEGIN SELECT COUNT(*) INTO num FROM student WHERE gender = s_gender; END // DELIMITER ; 下面选项中,能对上述存储过程实现正确调用的是 A. DECLARE @num; CALL CountProc1(in "女",out @num); B. SET @num; CALL CountProc1("女",@num); C. DECLARE @num; DECLARE CountProc1("女",out @num); D. DECLARE @num; CALL CountProc1("女",@num);