根据对话内容，从对话后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。
Tom: My boss told me never to go to work again.
Bob: 1 . Why?
Tom: I don't know. When he told me that, I was so confused.
Bob: Did you usually go to work late?
Tom: 2
Bob: When you did your work, 3
Tom: Sometimes.
Bob: How often did you look at the clock on the wall?
Tom: 4
Bob: Could you use a computer?
Tom: No, I can only use a typewriter.
Bob: Well, I think I know why. You did not use your time well. You didn't plan things well. 5 .
Tom: I see. I think I must work harder and learn to use a computer soon.
A. Did you get hurt?
B. Every ten minutes.
C. I can't believe it.
D. did you think about other things?
E. Well, I often did!
F. Don't tell a lie.
G. You didn't learn new things.
，变阻器R2的阻值变化范围是0～20
。开关S闭合，当变阻器滑片P由a端滑至b端过程中电压表示数的变化范围为
