系统具有随环境的改变而改变其结构和功能的能力。从系统的特征来看，这是指（）。
A.整体性
B.层次性
C.目的性
D.适应性
参考答案：A
左、右头臂静脉汇合处称静脉角。
Mary A Contrary has a SHORT position in 15 November heating oil contracts. She buys 15 December heating oil contracts. Ms. Contrary has:()
A. closed her futures position by offset.
B. initiated a new LONG futures position in addition to her existing SHORT position.
C. initiated an exchange-for-physicals (EFP).
