[单选题]Our country _____ great changes in the last 30 years.A. has experienced B. experiencedC. experimented D. has experimented
[单选题]Space exploration began in the 1960s, and since then about five hundred people _______ into space. [ ]A. are travelingB. traveledC. had traveledD. have traveled
[单选题]天然蛋白质水解的最终产物是α-氨基酸,结构如图所示,下列有关α-氨基酸的说法中错误的是R— CH-COOHNH2A.α-氨基酸既能与酸反应,又能与碱反应B.α-氨基酸在酸溶液中主要以阳离子形式存在C.α-氨基酸在碱溶液中主要以阴离子形式存在D.α-氨基酸难溶于水
[单选题]下列说法正确的是( )A.软脂酸甘油酯可使溴水褪色B.植物油可使溴水褪色C.甘油可使溴水褪色D.直接分馏得到的汽油可使溴水褪色
[单选题]Frank, with his two sisters , ______London by train which ______at 8:30 tomorrow morning .[ ]A. is leaving for ; will leave B. are leaving for ; leaves C. is leaving for ; leaves D. will leave for ; will leave
[单选题]I’m glad to see your health ______ after the operation.A.picking upB.setting upC.taking upD.getting up
[单选题]下列关于油脂的叙述,不正确的是[ ]A.油脂属于酯类B.油脂没有固定的熔沸点C.油脂是高级脂肪酸的甘油酯 D.油脂不能使溴水褪色
[单选题]使蛋白质从水溶液中析出而又不变质的方法是[ ]A.过滤B.加入硫酸铵溶液 C.加入福尔马林溶液D.分液
[单选题]通常情况下,用到的下列反应试剂所发生的反应,能使反应物碳链缩短的是A.氢氧化钠的水溶液B.氢氧化铜碱性悬浊液C.溴的四氯化碳溶液D.氢气(镍作催化剂)
[单选题]— Do you know our town at all— No, this is the first time I?_____ here. ( )A. have come B. was C. came D. am coming
[单选题]不同的运动员对运动鞋有不同的要求,为此,设计师采用最新的化学材料设计了各种性能的运动鞋,颇受运动员的青睐,篮球、排球运动员需要有一定弹跳性的鞋,故使用弹性十分好的顺丁橡胶作鞋底;足球运动员要求鞋能适应快攻、快停,且坚实耐用,使用强度十分高的聚氨酯橡胶作底材,并安上聚氨酯防滑订;田径运动员要求鞋柔软而富有弹性,为此,又设计了高弹性的聚异戊橡胶鞋底,以满足运动员的要求.下列单体能在一定条件下发生加聚反应生成 (聚异戊二烯)的是 [ ]A.丙烯 B.2-甲基-2 -丁烯C.乙烯和丙烯 D.2-甲基一1,3-丁二烯
[单选题]下列说法正确的是 A.已知PM2.5是指大气中直径≤2.5×10-6m的颗粒物,则PM为2.5的大气一定能产生丁达尔现象B.为提高农作物的产量和质量,应大量使用化肥和农药C.H、H是制造氢弹的原料,它们是同一种核素D.太阳能电池可采用硅材料制作,其应用有利于环保、节能
[单选题]A. you can see, the number of cars on our roads ______ rising these days. ( )A. was keeping B. keep C. keeps D. were keeping
[单选题]He dressed quickly, ______ hurriedly, grabbed his briefcase and hurried off down the hotel corridor. ( )A. shaveB. shavingC. to shave D. shaved
[单选题]下列药品中,可以治疗感冒的是 [ ]A.阿司匹林B.青霉素 C.胃平 D.麻黄碱
[单选题]A.poet and artist?_____ coming to speak to us about Chinese literature and painting tomorrow afternoon. [ ]A. isB. are C. was D. were
[单选题]I have to see the doctor because I ________ a lot lately.[ ]A. have been coughingB. had coughedC. coughedD. cough
[单选题]Weve spent too much money recently. — Well, it isnt surprising. Our friend and relatives _____ around all the time.A. are coming B. had come C. were coming D. have been coming
[单选题]Great changes ________in my hometown and some new buildings ________.[ ]A.have taken place;have appearedB.have been taken place;have appearedC.have taken place;have been appearedD.were taken place;were appeared
[单选题]海水是一个巨大的化学资源库,期待着人们的开发和利用.下列有关海水综合利用的说法不正确的是( )A.海水中含有溴元素,需经过化学变化才可以得到溴单质B.海水蒸发制海盐的过程中只发生了物理变化C.从海水中可以得到MgCl2,电解熔融MgCl2可制备MgD.利用潮汐发电是将化学能转化为电能
[单选题]下面食谱营养搭配最均衡的是( )A.凉拌青菜、土豆丝、馒头B.糖醋排骨、清蒸鲈鱼、米饭C.虾仁白菜、红烧带鱼、酸菜炖猪蹄、萝卜汤D.酱牛肉、炒油菜、红烧豆腐、西红柿蛋汤、馒头