题目

The Spotlightin Rio  Phelps puts spotlight on cupping（拔火罐）     Olympic gold medalist Michael Phelps fed American swimmers t0 8 gofd medal in the  4xiOO-meter relay, but .what grabbed media attention and led to stories and photos around the globe were the purple and red circles on his back     Michael Phelps of the USA is seen with red cupping marks on h/s shoulder as he competes  during the 2016 Rio Olympics men's 200m butterfly in Rio de Janeiro, Brazil , Aug 8,2016 Chinese swimmer Fu Yuanhui goes viral     Chain's women's swimmer Fu Yuanhui has created a sensa如下图所示，A、B为两个独立电源的路端电压和总电流I的关系图线，则下列说法中正确的是（    ） A．路端电压都为U0时，它们的外电阻相等 B．电流都是I0时，两电源的内电压相等 C．电源A的电动势大于电源B的电动势 D．电源A的内阻小于电源B的内阻