有关计划生育工作应该是
A.有计划地生育子女
B.晚婚、晚育和优生优育
C.有利于保护母亲和对儿童教育
D.提倡一对夫妇只生一个孩子
E.可以提高人口素质
参考答案:A,B,C,D,E
— Is Jack on duty today?
— It ________ be him. It's his turn tomorrow.
A.mustn't
B.won't
C.can't
D.needn't
造成非同期并列的可能原因有哪些?