题目

Photography has come a long way since the death of Mathew Brady. Today every part of life has been or is being photographed. One famous photographers of recent times is a woman-Margaret Bourke-White. Miss Bourke-White did not intend to be a photographer. She took pictures while in college to earn money. She began her career by photographing big factories and construction jobs. This kind of photography has remained her first love all her life. She sees great beauty in the common sight of a building being constructed or a bridge crossing a river. As a young girl, Margaret Bourke-White设飞机飞行中所受阻力与其速度的立方成正比，如飞机以速度v匀速水平飞行时，其发动机的功率为P，则飞机以2v速度匀速水平飞行时，其发动机的功率为（　　）A．8PB．4PC．16PD．2P