题目

下列离子方程式正确的是 A．向沸水中滴加FeCl3溶液制备Fe(OH)3胶体：Fe3+＋3H2OFe(OH)3↓＋3H+ B．向小苏打溶液中加入过量的石灰水：Ca2++OH－+HCO3－=CaCO3↓+H2O C．向硫酸氢钠溶液中加入氢氧化钡使溶液呈中性：Ba2++OH－+H++SO42－= BaSO4↓+H2O D．用食醋除去水壶中的水垢：CaCO3+2H+=Ca2++CO2↑+H2O 答案：BTwenty years ago,kids in school had never even heard of the Internet.Now,I'll bet you can't find a　36　person in your school who hasn't　37　heard of it.In fact,many of us use it on a regular basis and can even use it at　38　.The “net” in Internet really stands for network.A network is two or more computers　39　together so that information can be?　40　?or sent from one computer to　41　.The Internet is a vast　42　for all types of information.?You may enjoy using it to do　43　for a school project,downloading your favorite songs or　44　with friends and family.Information can be found　45 web pages that companies, organizations, and individuals(个人)create.It's like a giant bulletin board that the whole world uses!But since anyone can put　46　on the Internet,you also have to be careful and use your best　47　and a little common sense.?Just　48　you read something on a piece of paper someone puts on a bulletin board doesn't mean that it's good information,or even correct, for that matter.You have to be sure that whoever posted the information knows what they're talking about,　49　 if you're doing research!But what if you're just e?mailing people?You still have to be very　50　if you've never met the person that you're communicating with online.You could be doing something　51　!You should never give out any　52　 information to someone you don't know,not even your name!And just like you can't　53　the information on every website out there.You can't　54　on what strangers you “meet”on the Internet tell you either.In the same way that you could　55　things about yourself to tell someone,someone else could do the same to you!?36. A. stupid   B. single  C. common     D. clever?37. A. at least B. at mostC. at last  D. at first?38. A. school  B. Home C. work   D. hospital?39. A. met      B. Communicated   C. joined D. connected?40. A. shared  B. found  C. made  D. chosen?41. A. other    B. the other    C. another      D. others?42. A. material       B. resource     C. source D. matter?43. A. homework   B. housework  C. research     D. experiments?44. A. playing B. talking       C. meeting      D. communicating?45. A. through       B. across C. by      D. on?46. A. something    B. anything     C. everything  D. nothing?47. A. wisdom       B. judgmentC. Courage  D. confidence?48. A. because B. when  C. where D. what?49. A. specially      B. especially   C. naturally    D. strangely50. A. careful  B. wise    C. suspicious   D. confident?51. A. exciting       B. interesting  C. suspicious   D. confident?52. A. social   B. personal     C. general       D. special?53. A. respect  B. consult       C. send    D. believe?54. A. rely      B. believe       C. trust    D. base?55. A. make of       B. make from C. make out    D. make up??