— Look! The light in Mr. Brown's office is still on. He ___________ be working there.
— It ___________ be him. He has gone to America.
A:must; mustn't
B:can; mustn't
C:must; can't
D:can; can't
读长江水系示意图,对各河段的描述,正确的是( )
下列史实与法兰西第三共和国覆亡无关的是( )
把甲、乙两段电阻线接在相同的电压下,甲线中的电流大于乙线中的电流,忽略温度的影响,下列判断中错误的是 ( )