完形填空。 Jimmy is very 1 at math. Mary, his sister, doesn't do well 2 it. Jimmy often helps her with her math. One night, Jimmy and Mary take out their exercise books and begin 3 their homework. Soon Jimmy finishes 4 his homework, but his sister 5 . She can't work 6 the last problem. 'Let me 7 you. says Jimmy. 'No, please 8 . I'll do it myself. ', says Mary. She thinks and thinks, and an hour later she 9 it out. She is very tired, but she is very 10 . (     )1. A. good (     )2. A. at (     )3. A. to make (     )4. A. do (     )5. A. doesn't (     )6. A. on (     )7. A. help (     )8. A. isn't (     )9. A. finds (     )10. A. sorry B. better B. in B. do B. to do B. don't B. out B. to speak B. couldn't B. works B. bad C. fine C. on C. to do C. did C. needn't C. at C. helping C. can't C. looks C. happy D. well D. of D. to get D. doing D. can't D. for D. to tell D. don't D. does D. angry