合同的成立应具备（）两个阶段。
A.意思表示和订立
B.要约和订立
C.邀请和承诺
D.要约和承诺
参考答案：D
Many parents made their daily routine to get out for a walk in the evening.
A．this
B．it
C．that
D．what
何谓危险性病虫害？
