填空。 Flies (苍蝇) usually live in the dirty places. Let's look at a fly, and see where it 1 . First, it flies out of the window, 2 it stands on 3 dirty things in the street, and then it flies back to the house and walks over your 4 . When a fly walks on the dirty things in the street, its 5 have got some germs 6 them. When the fly walks on your food with its dirty feet, it 7 the germs on your food. What can you 8 this? First, we learn that we mustn't leave dirty things in the street or on the ground near 9 . Second, we learn that all food must be covered so that flies may not 10 it. Third, we learn that flies often carry germs and we must kill them as soon as we see them. (     ) 1. A. walks (     ) 2. A. first (     ) 3. A. some (     ) 4. A. food (     ) 5. A. body (     ) 6. A. in (     ) 7. A. carries (     ) 8. A. study from (     ) 9. A. the factory (     ) 10. A. arrive B. stands B. second B. any B. drink B. feet B. to B. has B. study for B. our door B. get C. lives C. third C. every C. cups C. eyes C. on C. leaves C. learn for C. our house C. arrive in D. flies D. fourth D. each D. bowls D. head D. over D. takes D. learn from D. a window D. get to