题目

Two American scientists told the people in industrial nations that they would be much healthier if they ate more of the same kind of foods eaten by humans living more than 10,000 years ago． The scientists say that the human body has changed very little since human first appeared on earth, but the way we live has changed greatly．Our body has not been able to deal with these changes in life style and this has led to new kinds of sicknesses．These new sicknesses were not known in ancient times．So they are called “diseases of civilization （文明）”．Many cancers and diseases of th一质量为m的小球，用长为L的轻绳悬挂于O点，小球在水平力F的作用下，开始由平衡位置P点缓慢的移动到Q点，此时绳与竖直方向的偏角为θ，如图所示，则力F所做的功为 A、mgLcosθ      B、FLsinθ    C 、mgL(1-cosθ)     D、FL(1-cosθ)