题目

如图所示，A1和A2是两块相同的电流表，V1和V2是两块相同的电压表.电流表A1的示数是1.4 mA，电压表V1和V2的示数分别是0.8 V和0.6 V.则电流表A2示数__________；电压表和电流表的内阻之比__________. 答案：0.6 mA；3:1— Must we clean the room right now?      — No, you _____. You _____ clean it after lunch.  [     ]A. needn't; may B. needn't; must C. mustn't; can D. mustn't; may