题目

The reason ________ he gave for his being away for such a long time is ________ his mother was ill. A . why; that B . that; that C . that; because D . why; because 答案：B某次实验中，李明同学连接了如图所示的电路，若电源电压为6V，且保持不变，电阻R1=8Ω，滑动变阻器R2的最大阻值为10Ω．他所选用的电压表量程为0～3V，电流表量程为0～0.6A．为了保证电路安全，实验中滑动变阻器接入电路的阻值范围是（ ）A．0～2ΩB．0～8ΩC．2Ω～8ΩD．8Ω～10Ω