已知Fe(OH)3胶粒带正电荷，Al(OH)3胶粒也带正电荷，而H2SiO3胶粒带负电荷，带不同电荷的胶体相互混合时，则发生聚沉现象。将某液体逐滴加入Fe(OH)3溶胶内，开始时产生沉淀，继续滴加时沉淀溶解，该液体是[ ]
A．2 mol/L H2SO4溶液
B．2 mol/L NaOH溶液
C．2 mol/L MgSO4溶液
D．硅酸溶胶
答案：A
| 完型填空。 | |||
| In the United States there was an unusual story telling of the daughter of a mechanic(技工). One day while walking along the bank of a lake, the girl 1 to see 20 eggs laid by a wild goose(鹅). After some time the girl 2 the mother would not return to her eggs and she 3 to take them home. There she carefully 4 the eggs in the heat of a lamp. Several days 5 the eggs broke and the baby geese came into the 6 . Geese are known to take the first living thing they see as their mother. 7 , to these young geese, the girl was their mother. As they 8 , the girl was able to 9 her birds to run across the grass, but she could not teach them to 10 . The girl became increasingly worried about this, both when 11 and in her dreams. Later, she had an 12 : She would pilot a plane to guide them in 13 . She asked her father for a plane and he assembled （组装） a small aircraft for her. Caring about 14 safety, the father decided to pilot the plane himself. However, the birds did not __15__ or follow him, and 16 slept in the grass. One day, the girl 17 into the plane, started it and soon left the 18 . Seeing their mother take to the air, the birds 19 flapped（拍打） their wings and 20 . She flew the plane freely in the sky, her young birds following. | |||
| ( )1. A. managed ( )2. A. realized ( )3. A. helped ( )4. A. placed ( )5. A. ago ( )6. A. family ( )7. A. But ( )8. A. increased ( )9. A. ask ( )10. A. fly ( )11. A. asleep ( )12. A. idea ( )13. A. air ( )14. A. his ( )15. A. respect ( )16. A. so ( )17. A. climbed ( )18. A. house ( )19. A. secretly ( )20. A. looked away | B. Attempted B. expected B. decided B. protected B. out B. lake B. Also B. improved B. lead B. race B. away B. opinion B. space B. her B. remember B. instead B. looked B. floor B. disappointedly B. set out | C. Happened C. imagined C. afforded C. treated C. later C. home C. Thus C. rose C. want C. swim C. around C. explanation C. flight C. their C. recognize C. hardly C. reached C. water C. patiently C. went by | D. supposed D. admitted D. meant D. examined D. long D. world D. Still D. grew D. allow D. sing D. awake D. excuse D. plane D. its D. receive D. too D. fell D. ground D. eagerly D.turned back |