题目

如图所示，R1为定值电阻，R2是负温度系数电阻的热敏电阻，L为小灯泡，当温度下降时，（      ）                                                                                                          　   A．R1两端的电压增大          B． 电流表的示数增大　   C．小灯泡的亮度变强           D． 小灯泡的亮度变弱                                                                                                                                       答案：C

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