[单选题]My daughter _____ hard for more than one year to realize her dream joining the Party and now her dream comes true.A. works B. is working C. has worked D. worked
[单选题]下列说法正确的是[ ]A.“乙醇汽油”是在汽油中加入乙醇生成的一种新化合物 B.淀粉、纤维素完全水解的产物互为同分异构体C.鸡蛋清中加入CuSO4溶液会产生盐析 D.煤油是石油的分馏产品,可用于保存少量金属钠
[单选题]蛋白质在胃蛋白酶和胰蛋白酶的作用下变成氨基酸的反应属于 ( )A.消去反应B.聚合反应 C.水解反应D.酯化反应
[单选题]The paper _____ soft _____ easily.[ ]A. feeling; tearsB. to feel; is tornC. felt; tore D. to be felt; tears
[单选题]Because the shop ______, all the clothes are sold at half price.[ ]A. has closed downB. closed downC. is closing down D. had closed down
[单选题]绿色化学提倡化工生产应提高原子利用率.在下列制备环氧乙烷的反应中,原子利用率最高的是 [ ]A.CH, =CH2+CH,-O一H(过氧乙酸)CH-CH,+CH, COOH0B.CH2=CH2+Cl2+Ca(OH)2→CH2-CH20+CaCl2+H2O C.3CH2CB北剂叫HCH2OHOH+ HOCH2CH2-O-CH2CH2OH+2H2OD.2CH2=CH2?+?O2催化剂2CH,-CH0
[单选题]有关自然资源开发利用的一些说法中,正确的是( )①海水淡化与化工生产、能源技术相结合是海水综合利用的重要方向②甲烷水合物被认为是21世纪新型洁净能源,目前已成为各国关注和研究的重要领域③石油化工中的合成材料(常用塑料)在自然环境中容易降解④我国在哥本哈根气候变化大会上作出大规模减排温室气体的承诺,温室气体是指SO2气体⑤绿色合成提倡尽可能使用无毒、无害原料,可再生资源等.A.②③④B.①④⑤C.①②⑤D.①③⑤
[单选题]煤的气化和液化是煤高效、洁净利用的方向之一.下图为加强热某地煤样品所得煤气组成及体积分数随温度变化的曲线图.由图可知该煤气中[ ?]A.只含有碳、氢两种元素 B.所含的有机物是CH4、CnHm、COC.CO体积分数小于CH4体积分数D.氢气体积分数最大
[单选题]— This returned scientist has become one of the top experts in his field.— Yes, I know him very well. He once _____ in South America with wild animals for eight years.A. has worked B. worked C. had worked D. has been working
[单选题]冶炼金属一般有下列四种方法:①焦炭法;②水煤气法;③活泼金属置换法;④电解法.古代有:(I)火烧孔雀石炼铜;(Ⅱ)湿法炼铜.现代有:(Ⅲ)铝热法炼铬;(Ⅳ)从光卤石中炼镁.对它们的冶炼方法的分析,不正确的是[ ]A.Ⅰ,① B.Ⅱ,②C.Ⅲ,③ D.Ⅳ,④
[单选题]在人体的血液中,如果钾元素的含量偏高会引起心脏衰竭,甚至死亡;如果钾元素的含量偏低会影响肌肉和神经的功能,这时就需要补充钾.一种医用含钾化合物的水溶液能跟硝酸银溶液反应生成不溶于稀硝酸的白色沉淀.该化合物是 [ ]A.KNO3B.K2CO3 C.KCl D.KOH
[单选题]下列说法中错误的是[ ]A.在豆浆中加少量石膏,能使豆浆凝结为豆腐 B.误服可溶性重金属盐,可立即服用大量牛奶或鸡蛋清 C.用灼烧的方法可鉴别毛织物和棉织物D.温度越高,酶对某些化学反应的催化性能越好
[单选题]Not until I began to work ________ how much time I had wasted. ?[ ]A. did I realizeB. didnt I realizeC. hadnt I realizedD. had I realized
[单选题]据人民网报道,有一集团将在太空建立巨大的集光装置,把太阳光变成激光用于分解海水制氢,其反应可表示为:.有下列几种说法:① 水分解反是放热反应;② 氢气是一级能源;③ 使用氢气作燃料有助于控制温室效应;④ 若用生成的氢气与空气中多余的二氧化碳反应生成甲醇储存起来,可改善生存条件.其中叙述正确的是[ ]A.①② B.②③C.③④ D.①②③④
[单选题]下列有关物质用途的说法正确的是A.碳酸钠治疗胃酸过多B.稀硫酸除铁锈C.晶体硅用于制光导纤维D.二氧化硫用于漂白滋补品银耳
[单选题]Though three football players of the opposite sideto prevent Robert from kicking the ball, he still ______ to shoot the ball into the goal.A.tried; managedB.managed; triedC.tried; triedD.managed; managed
[单选题]Frank insisted that he _____ asleep I had great difficulty in waking him up.A. was notB. shouldnt be C. were not D. shant
[单选题]— A.e you still very busy— ?Yes, I the report for the manager and it wont take long. [ ]A. have just finishedB. am just finishingC. had just finishedD. am just going to finish
[单选题]We ____ the task by the time he came to help us.[ ]A. had finishedB. finishedC. finish D. will have finished
[单选题]The hunterhis gun under the tree where he was .A.lay; lieingB.laid; lyingC.lied; layingD.lay; lying
[多选题]下列关于蛋白质的叙述中不正确的是( )A.蛋白质溶液中加入饱和硫酸铵溶液,蛋白质析出,如再加水也不溶解 B.蛋白质分子能透过滤纸,但不能透过半透膜C.重金属盐使蛋白质变性,所以吞服“钡餐”会引起中毒D.浓硝酸溅在皮肤上,能使皮肤呈黄色是因为蛋白质和浓硝酸发生反应