— If the traffic hadn't been so heavy, I could have been back by 6 o'clock.

— What a pity! Tina _____ here to see you.[ ]

A. is

B. was

C. would be

D. has been

欧姆定律的公式可以写成U=IR，因此可以说电阻两端的电压与电流成（）比。