题干

合金具有优良的物理、化学或机械性能,因而应用广泛.下列物质属于合金的是(  )

A:钢铁

B:水银

C:水晶

D:金刚石

上一题 下一题 0.0难度 选择题 更新时间:2019-08-23 12:46:16

答案(点此获取答案解析)

A

同类题2

根据短文内容, 从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    A major source of teen stress is school exams,and test anxiety is not uncommon.When you recognize your teen is under stress,how can parents help your teen stay calm before an exam?

    Be involved.Parents need to be involved in their teen's work. ____ What they look for is your presence­to talk,to cry,or simply to sit with them quietly.Communicate openly with your teen.Encourage your teen to express his/her worries and fears,but don't let them focus on those fears.

    Help them get organized.____ Together,you and your teen can work out a time­table in which he/she can study for what he/she knows will be on the test.

    Provide a calm setting.Help your teen set up a quiet place to study and protect his/her privacy.Give them a nutritious diet.It's important for your teen to eat a healthy,balanced diet during exam times to focus and do his/her best.____ If this happens,encourage your teen to eat light meals or sandwiches.A healthy diet,rather than junk food,is best for reducing stress.

    ____ Persuade your teenager to get some sleep and/or do something active when she needs a real break from studying.Making time for relaxation,fun,and exercise are all important in reducing stress.Help your teen balance her time so that she will feel comfortable taking time out from studying to spend time with friends or rest.

    Show a positive attitude.____Your panic,anxiety and blame contribute to your teen's pressure.Make your teen feel accepted and valued for his/her efforts.Most importantly,reassure your teen that things will be all right,no matter what the results are.

A.A parent's attitude will dictate their teen's emotions.

B.Exam stress can make some teens lose their appetite.

C.They will only make the situation worse.

D.Encourage your teen to relax.

E.The best thing is simply to listen.

F.Help your teen think about what he/she has to study and plan accordingly.

G.Your teen may also make negative comments about themselves.

同类题4

阅读理解、分析。

        伽比萨城一个年轻的医科大学生,正在大教堂里跪着祈祷。除了一条链条扰人的擦碰声,大厅里一片寂静。一个教堂司事,刚注满一盏从教堂顶上悬挂下来的油灯,漫不经心地让它在空中来回摆动。摆动着的挂灯链条的前喀声惊扰了这个学生,引起他一连串的思考。

        突然,他跳起身来,这一举动使其他礼拜者大为惊讶。在摆动着的油灯的节奏中,他仿佛遭到了闪光的突然袭击。他觉得链条的节奏似乎是有规律的,那盏前喀作响的挂灯每往返摆一次用的时间似乎一样长,尽管往返的距离越来越小。

        他的感觉正确吗?如果正确,那他就是发现了奇迹。他决定立刻回家,马上去弄明白究竟是看花了眼,还是发现了大自然的一个伟大真理。

        他一到家,就找来两根同样长的绳索,各坠上一块重量相同的铅块,将两条绳索分别系在不同的厅柱上,准备做他的实验。他请他的教父穆契柯·铁达迪帮助他进行这个实验:"你数这条绳索的摆动次数,我数那一条。"

        老头子耸一耸肩。"又是伽利略一个发疯的念头。"他咕哝着,但是他同意帮忙。

        伽利略手拿两个铅摆,将一个拉到距垂直线四手掌宽的位置,另一个拉到两手掌宽的位置,然后同时放开手。两个人分别数了两条绳索的来回次数,然后加以比较。总数是一样的,各为100次。两条绳索的起点虽大不相同,但在同样时间内到达同样的点上。

        就这样,从教堂的油灯的摆动中,伽利略发现了自然的节奏原则。今天,这项原则已应用于时钟计时、计数脉搏。计算日食和推算星辰的运动等方面。