最典型的神经毒类毒蛇有()
A.眼镜蛇
B.眼镜王蛇
C.蝮蛇
D.烙铁头蛇
E.银环蛇
参考答案:E
在如图所示的电路中,R1、R2和R3皆为定值电阻,电源的电动势为E,内阻为r。设理想电流表A的读数为I,理想电压表V的读数为U。当R1发生断路时
A.I变大,U变小,R3的功率不变
B.I变大,U变大,R3的功率增大
C.I变小,U变大,R3的功率增大
D.I变小,U变小,R3的功率减小
The kids enjoy eating junk food, ______ their parents don't let them eat often. [ ]
A. so
B. or
C. and
D. but