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Starving polar bears are eating one another in the Arctic. Flowers are blooming too soon and die. The ice caps are melting so fast that rising water levels will threaten coastal towns along Florida within several decades. These are just a few examples of the terrible consequences of climate change supported by a new analysis in Nature.    In the past three decades, average global temperatures have risen about 0. 6°C and are projected to jump by about 1. 7°C by the end of the century, says Cynthia Rosenzweig, who leads the Climate Impacts Group at NASA’s Goddard Institute for Space Studi有一电路连接如图所示,理想变压器初级线圈接电压一定的交流电,则下列说法中正确的是 [     ]A.只将S1从2拨向1时,电流表示数变小 B.只将S2从4拨向3时,电流表示数变小 C.只将S3从闭合变为断开,电阻R2两端电压增大 D.只将变阻器R3的滑动触头上移,变压器的输入功率增大
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