20 1 1 Since the beginning of summer, continuous high temperature and little rain have occurred in parts of Guizhou, Yunnan, Chongqing and other provinces and cities in southern China, resulting in di

20 1 1 Since the beginning of summer, continuous high temperature and little rain have occurred in parts of Guizhou, Yunnan, Chongqing and other provinces and cities in southern China, resulting in different degrees of drought. A, because the number of turns is constant, the output voltage of the step-up transformer is constant, so A is wrong;

B, the output voltage of the step-down transformer is the voltage at both ends of the user, so B is wrong;

C, the output power increases, the current on the transmission line increases, and the power loss on the transmission line increases, so c is correct;

D, the ratio of power loss to total power on the transmission line = △U? U = IR U, where I increases and U remains unchanged, so the proportion increases, so D is correct;

So choose CD.