完形填空。 In Twain, many people know what a 'motorpool' means. It is 1 known as a place for the maintenance (维修) of official business and government cars. 2 it is a place for vehicle maintenance. More than ten years ago I came to America on business and I took advantage of the 3 to visit my friend. My friend drove a car to 4 me at the airport, and took me to his home. Out of the 5 , my friend drove his car into the innermost 6 , which had a sign 'carpool only'. I 7 what 'carpool' meant. I felt doubted whether he was going to a motorpool. 8 I thought myself clever in asking: 'Is there anything wrong with the car?' 'Nothing. 9 ?' said he. 'Well then, why are you going to carpool?' I 10 . My friend couldn't help 11 and told me that 'carpool' refers to the lane that only the cars with two or more 12 can drive in. I felt rather embarrassed on 13 that. After dinner, my friend's neighbor came over to ask whether he 14 'carpool' the next day. ' 15 ,' my friend said, 'I will accompany my friend to go shopping tomorrow.' I was 16 again, wondering why he could not 'carpool' with him since we had 'carpooled' 17 . My friend explained to me again that the 'carpool' that his neighbor 18 meant they in turn drove the car to work so as to save energy. The first 'carpool' is a noun, 19 the second 'carpool' is a verb. It is really 20 for newcomers in America to understand it in a short time. (     )1. A. commonly (     )2. A. In general (     )3. A. break (     )4. A. watch (     )5. A. house (     )6. A. road (     )7. A. wondered (     )8. A. For (     )9. A. How (     )10. A. replied (     )11. A. saying (     )12. A. passengers (     )13. A. noticing (     )14. A. needed (     )15. A. Sure (     )16. A. believed (     )17. A. today (     )18. A. used (     )19. A. as (     )20. A. interesting B. probably B. In particular B. time B. help B. airport B. lane B. knew B. Thus B. What B. asked B. talking B. drivers B. seeing B. could B. Sorry B. doubted B. tomorrow B. insisted B. so B. difficult C. partly C. First of all C. chance C. meet C. station C. street C. understood C. Then C. Why C. explained C. laughing C. gentlemen C. informing C. should C. Pardon C. confused C. yesterday C. learned C. while C. important D. simply D. Above of all D. place D. catch D. waiting-room D. route D. learned D. Though D. Where D. answered D. speaking D. ladies D. hearing D. would D. Good D. worried D. tonight D. provided D. for D. necessary