题目

The Oregonian(俄勒冈报) is the daily newspaper for the state of Oregon where the Hagens live. Since it is published in the largest city, which is Portland, most of the readers live within 50 miles of Portland.      From Monday to Saturday, the paper has about 75 pages, of which 20 pages are advertisements. It normally has 5 sections which are called Nation, Sports, Metro(大都会), Living and Business.      Nation is national news mostly with some international news about earthquakes, floods, and tensions(紧张)around the world. Sports cover the professional sports in season, col下面关于功、功率、机械效率的说法中正确的是： [     ]A. 功率大的机器做功一定快 B. 功率反映了能量转化的快慢C. 机器做功少，功率一定小，机械效率一定低D. 有用功一定时，消耗额外功少的机械，机械效率高