武昌起义后，清政府起用袁世凯的直接原因是

A．袁世凯手握兵权

B． * * 南方民主革命的需要

C．维护清朝封建专制统治的需要

D．适应帝国主义列强的要求

An analyst does research about options. A series of interest rate call options expiring on different dates but having the same exercise rate is best characterized as a(n):

A. zero-cost collar.
B. interest rate cap.
C. interest rate floor.