题目

?Could you_____,please??No problem.A.pass the pen meB.pass me to the penC.pass me the pen 答案：【答案】C【解析】句意：请你递给我那只钢笔好吗？没问题。pass sb sth=pass sth to sb把某物递给某人；故选C。如图，电源电压保持不变，电阻R1的阻值为20Ω．闭合开关，通过R1的电流为0.3A，干路总电流为0.5A．求：（1）电源电压；（2）电阻R2的值；（3）通电10s，电流通过电阻R2做的功．