串联管路
参考答案：
不同直径管段彼此首尾相接所组成的管路系统。
—Did you have a______time______ in the park?
—Yes. I enjoyed myself very much. [ ]
A. good; playing
B. nice; walk
C. pleasant; to walk
D. pleased; playing
导体的电阻是导体的固有特性，与外加电压无关。
