完形填空。 Jimmy is very __ 1 __ at Math. Mary, his sister, doesn't do well __ 2 __ it. Jimmy often helps her with math. One night, Jimmy and Mary take out their exercise-books and begin __ 3 __ their lessons. Soon Jim my finishes __ 4 __ his homework, but his sister __ 5 __ . she cant' work __ 6 __ the last problem. 'Let me __ 7 __ you,' say Jimmy. 'No, please __ 8 __ . I'll do it myself,' says Mary. She thinks and thinks, an hour later she __ 9 __ it out. She is very tired, but very __ 10 __ . (     ) 1. A. good (     ) 2. A. at (     ) 3. A. to make (     ) 4. A. do (     ) 5. A. doesn't (     ) 6. A. on (     ) 7. A. to 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. help C. can't C. looks C. happy D. well D. of D. to get D. doing D. can't D. far D. to tell D. don't D. does D. angry