57的分子乘15，要使分数的大小不变，分母也乘15．即57=5×157×15．
故答案为：15．
图示电路，换路前Uc（0-）=0.2U1，UR（0-）=0，求电路换路后Uc（0+）和UR（0+）分别为：().
A.Uc(0+)=0.2U1，UR(0+)=0
B.Uc(0+)=0.2U1，UR(0+)=0.2U1
C.Uc(0+)=0.2U1，UR(0+)=0.8U1
D.Uc(0+)=0.2U1，UR(0+)=U1
According to this passage, thinking that one can fly might be an example of ______
A．medicine overdose
B．being out of touch with reality
C．recovering normal functioning
D．symptom control
