题目

如图所示为一组合逻辑电路，其中，电阻R1、R2较小。当A为0，B为0时，F为（ ） A . 0 B . 1 C . 无法确定 D . 矩形脉冲信号 答案：CMy uncle _________in a documentar about the Hutongs in Beijing last month. But I don't know if he has finished it.A.acted B.has acted C.was acting D.is acting