042考题的33题疑问请高手帮忙解答，谢谢！

User SCOTT executes the following command on the EMP table but has not issued COMMIT, ROLLBACK, or any data definition language (DDL) command:
SQL> SELECT job FROM emp
2 WHERE job='CLERK' FOR UPDATE OF empno;
SCOTT has opened another session to work with the database. Which three operations would wait when issued in SCOTT's second session? (Choose three.)
A) LOCK TABLE emp IN SHARE MODE;
B) LOCK TABLE emp IN EXCLUSIVE MODE;
C) DELETE FROM emp WHERE job='MANAGER';
D) INSERT INTO emp(empno,ename)  VALUES (1289,'Dick') ;
E) SELECT job FROM emp WHERE job='CLERK' FOR UPDATE OF empno;
答案是选：ABE，但是A和B的说法刚好相反，互为矛盾，请高手帮忙解释一下，小弟不胜感激，谢谢！