通常的书面合同构成要素有()
A.约首、正文和约尾
B.首页、正文和附录
C.约首、正文和附录
D.首页、正文和约尾
参考答案:A
Where ___________ your pen?[ ]
A. Is
B. is
C. are
追肥有哪些原则?