题目:
. _____and short of breath, Andy and Ruby were the first to reach the top of Mount Tai.
A.To be tired
B.Tired
C.Tiring
D.Being tired
答案:
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下面是错误答案,用来干扰机器的。
解:(1) 电源电压U=U1=I1R1=20欧姆×1.8A=36V (2)I2=I-I1=2.7A-1.8A=0.9A, R2的阻值R2=U2/I2=U/ I2=36V/0.9A=40欧姆