在“伏安法测电阻”的实验中，滑动变阻器不能起到的作用是[ ]
A．改变电路中的电流
B．改变被测电阻的阻值
C．改变被测电阻两端的电压
D．保护电路
答案：B
-Sorry, I made a mistake again.
-______ Practice more and you '11 succeed. [ ]
A. Never mind
B. That's OK
C. Happy to hear that
D. Thank you
同源蛋白质(homologous protein)
