题目

Sports cars such as Ferraris and Porsches are priced _____ the reach of most people. A．under       B．out    C．within       D．beyond 答案：D16．阻值为2Ω的电阻R1与阻值为5Ω的电阻R2并联起来接在电源上，R1、R2两端电压之比为1：1，电流之比为5：2．