[单选题]— What"s wrong with your coat— Just now when I wanted to get off the bus, the man next to me ____ on it.A. sat B. had sat C. had been sitting D. was sitting
[单选题]-Why didnt you turn up at the meeting-I ________ for a longdistance call from my father in England.[ ]A.waitedB.had waitedC.was waitingD.have been waiting
[单选题]下列说法不正确的是[ ]A.氟、氯、溴、碘都是海水中的常量元素B.蒸馏和蒸发分别可以从海水中得到淡水和粗盐C.海水是锂元素的一个重要来源D.世界上生产的镁大部分来自海水
[单选题]— Why didnt you answer the phone— Im terribly sorry,but the doorbell________,too.[ ]A. is ringingB. rangC. was ringingD. was about to ring
[单选题]以下叙述不正确的是 [ ]A.不锈钢是化合物 B.黄铜是合金 C.钛和钛合金是制造飞机轮胎的重要材料 D.铝是地壳中含量最多的金属元素
[单选题]新鲜水果、蔬菜、乳制品中富含的维生素C 具有明显的抗衰老作用,但易被空气氧化.某课外小组利用碘滴定法测某橙汁中维生素C的含量,其化学方程式如下 [ ]A.上述反应为取代反应 B.维生素C在酸性条件下水解得到2种产物 C.维生素C不可溶于水,可溶于有机溶剂D.维生素C的分子式为C6H8O6
[单选题]— Your job is well done. _____ you _____?for it— Yes. A.d I got extra $500 as a reward yesterday. ( )A. Have; paid B. Have; got paid C. Did, pay D. Are; paid
[单选题]By the time he realizes he _____ into a trap, itll be too late for him to do anything about it.A. walks B. walked C. has walked D. had walked
[单选题]工业废水中常含有不同类型的污染物,可采用不同的方法处理.以下处理措施和方法正确的是[ ] 污染物 处理措施 方法类别 A. 废酸 加生石灰中和 物理法 B.Cu2+等重金属离子 加硫酸盐沉降 化学法 C 含苯废水 用活性炭吸附 物理法 D. 含纯碱的废水 加石灰水反应 化学法
[单选题]— I ____ to be here on time, sir. — But you ____ late again. [ ]A. meant; are B. meant; had been C. have meant; were D. have meant; are
[单选题]坎昆世界气候大会全称《联合国气候变化框架公约》第16次缔约方会议暨《京都议定书》第6次缔约方会议,于2010年11月29日到12月10日在墨西哥海滨城市坎昆举行.《京都议定书》针对六种温室气体进行削减,包括二氧化碳(CO2)、甲烷(CH4)、氧化亚氮(N2O)、氢氟碳化物(HFCs)、全氟碳化物(PFCs)及六氟化硫(SF6).科学研究发现,同条件下等体积的甲烷产生的温室效应远强于二氧化碳的.下列说法正确的是[ ]A.等质量的二氧化碳产生温室效应比甲烷的强 B.天然气是清洁能源,燃烧天然气不对环境产生任何影响 C.二氧化碳对全球升温的贡献百分比最大,是因为二氧化碳含量较多D.氟利昂可作致冷剂,大量向空气中排放氟利昂,会使气温降低
[单选题]关于物质的用途下列说法正确的是 ①水玻璃是制备硅胶和木材防火剂的原料;②氢氧化铝可以用做耐火材料;③氢氟酸可以用来刻蚀玻璃;④纯净的二氧化硅是制备光导纤维的原料;⑤利用氯气的毒性可以消灭田鼠;⑥漂白粉既可做漂白棉麻纸张的漂白剂,又可做游泳池及环境的消毒剂;⑦四氧化三铁常用作红色油漆和涂料⑧晶体硅是良好的半导体材料,可以制成光电池A.①②③④⑤⑥B.①③④⑤⑥⑧ C.①②④⑤⑥⑦D.③④⑤⑥⑦⑧
[单选题]下列不属于复合材料的性能的是 ( )A.强度高B.密度大 C.耐高温D.耐腐蚀
[单选题]The writer and teacher Smith ______ through millions of ups and downs since he moved to Sydney. [ ]A. have goneB. had goneC. wentD. has gone
[单选题]Ive won a holiday for two to A.rica. I _______ my mum there.[ ]A. take B. am takingC. tookD. will be taking
[单选题]— Im sure A.drew will come out first in this gymnastic competition.— I think so. He ________ for it for months. [ ]A. is preparingB. was preparingC. had been preparingD. has been preparing
[单选题]We first met on a train in 2000. We both felt immediately that we _____ each other for years.A. knewB. have known C. had knownD. know
[单选题]某有机物的结构简式为它不可以发生的反应类型有:①取代 ②加成 ③消去 ④水解 ⑤酯化 ⑥中和⑦氧化 ⑧加聚 [ ]A.④⑦⑧B.①⑤⑦ C.⑧ D.①②
[单选题]下列关于天然物质水解的叙述正确的是( )A.油脂的水解反应都是皂化反应B.油脂的水解可得到甘油C.蛋白质水解的最终产物均为葡萄糖D.淀粉水解和纤维素水解得到的最终产物不同
[单选题]下列反应原理中,不符合工业冶炼金属实际情况的是 [ ]A.2HgO2Hg+O2↑ B.2Al+3MnO22Al2O3+3MnC.2MgO2Mg+O2↑ D.4CO+Fe3O43Fe+4CO2
[单选题]— Youve agreed to go.So arent you getting ready— But I ______ that you would have me start at once. [ ] A. didnt realize B. dont realize C. havent realized D. hadnt realized