[单选题]On her next birthday, Ann ________ married for twenty years.A. isB. has beenC. will beD. will have been
[单选题]空气污染已成为人类社会面临的重大威胁.下列气体中,不会造成空气污染的是[ ]A.N2B.Cl2C.SO2D.NO2
[单选题]— Has your former classmate come back from A.erica— Yes , he________there for eight years.[ ]A. has stayedB. staysC. stayedD. had stayed
[单选题]已知天然气的主要成分CH4是一种会产生温室效应的气体,等物质的量的CH4和CO2产生的温室效应,前者大.下面是有关天然气的几种叙述,其中正确的有 ①天然气与煤、柴油相比是较清洁的能源②等质量的CH4和CO2产生的温室效应也是前者大③燃烧天然气也是酸雨的成因之一 [ ]A.①②③ B.只有① C.①② D.③
[单选题]下列实验操作中,正确的( )A.取液体药品B.熄灭酒精灯C.给液体加热D.读液体的体积
[单选题]已知某氨基酸的相对分子质量小于200,且氧的质量分数约为0.5,则其分子中碳的个数最多为A.5个B.6个C.7个D.8个
[单选题]人生病时要合理用药.下列药品的选用合理的是( )A.碳酸镁:中和过多胃酸B.阿司匹林:消炎抗菌C.青霉素:解热镇痛D.医用碘酒:人体补碘
[单选题]下列有关新型高分子材料应用的说法不正确的是 [ ]A.高分子膜利用其选择性透过能力,可用于海水淡化、污染控制、物质制取与回收等方面 B.作为医用高分子材料制人造器官,必须考虑其与人体的相容性和机械性能 C.新型的聚乙烯醇是高吸水性高分子,具有与水生成易挥发的特性,所以称为“尿不湿” D.新材料研究正向智能化、高功能化的方向发展
[单选题]大气层外的臭氧层的主要作用是A.吸收CO2B.分解补充O2C.吸收红外线D.吸收紫外线
[单选题]I, as well as she, ____ your close friend. We will shareyour joys and sorrows. [ ]A. wasB. are C. is D. am
[单选题]— What a mistake! — Yes. I _____?his doing it another way, but without success.A. was suggesting B. will suggest C. would suggest D. had suggested
[单选题]下列关于牙膏的说法中不正确的是( )A.牙膏中加甘油作保湿剂B.用含氟牙膏刷牙可使牙齿坚固,从而有效防止蛀牙,故牙膏中的氟含量越高越好C.牙膏中的增香剂和甜味剂可改善牙膏的口感D.牙膏中的着色剂可使牙膏变白或呈现出不同的颜色
[单选题]下列叙述正确的是? [ ]A.稀硝酸、稀硫酸均能将木炭氧化成二氧化碳 B.Na2O2与水反应,红热的Fe与水蒸气反应均能生成碱 C.相同条件下,2mol氢原子所具有的能量小于1mol氢分子所具有的能量D.煤经气化和液化两个物理变化过程,可变为清洁能源
[单选题]居室空气污染的主要来源之一是人们使用的装饰材料、胶合板、内墙涂料会释放出一种刺激性气味的有机气体,它对人体极为有害.该气体是(?)A.甲烷B.氨气C.甲醛D.二氧化硫
[单选题]开发新材料是现代科技发展的方向之一,下列有关材料的说法正确的是[ ]A.氮化硅陶瓷是新型无机非金属材料 B.C60属于化合物,用于制造纳米材料C.纤维素乙酸酯属于天然高分子材料D.单晶硅常用于制造光导纤维
[单选题]— The telephone is ringing. — I ____ answer it. [ ]A. am going to B. am to C. will D. am about to
[单选题]新型镁合金被大量应用于制成笔记本电脑外壳、竞赛自行车框架等,这说明镁合金具有的优异性能是( )①熔点低②硬度大③延展性好④导电性强⑤密度小⑥耐腐蚀 A.①②③ B.②③④C.①③⑥D.②⑤⑥
[单选题]I would have come earlier,but I________that you were waiting for me.[ ]A.hadn’t knownB.didn’t knowC.would have knownD.haven’t known
[单选题]Steve Jobs, American former Apple CEO and founder, ______ a week after birth by Paul and Clara Jobs, was a person who changed the world. A.adjustedB.adoptedC.adaptedD.absorbed
[单选题]A. the party, Eric oughtnt to?_____ the joke. Didnt you see the principal was a bit _____? [ ]A. be telling; embarrassingB. tell;embarrassedC. havetold; embarrassingD. have told; embarrassed
[单选题]从海水中提取镁的主要流程是[ ]A.B.C.D.