半圆柱体P放在粗糙的水平地面上，其左、右端各有固定放置的竖起挡板M、N，在P和挡板之间放有光滑、质量分布均匀的小圆柱体a、b，两者质量相等，a的位置比b高，整体装置处于静止，如图所示是这个装置的纵截面图，下列判断正确的是( )

A. P对a的弹力比P对b的弹力小
B. P对a的弹力比P对b的弹力大
C. 挡板对a的弹力比挡板对b的弹力大
D. 挡板对a的弹力与挡板对b的弹力小

（题文）李克强说，中国对外开放的大门会越开越大，中国扩大开放本身就是为了维护和促进自由贸易体制，这也将为世界各国企业带来发展机遇。这是基于
①事物间的相互联系和相互作用构成事物的发展
②整个世界是一个普遍联系的有机整体
③重视量的积累就能实现事物的质变
④任何事物的发展都不是一帆风顺的
A. ①② B. ①③ C. ②④ D. ③④

如图甲所示为阿特武德机的示意图，它是早期测量重力加速度的器械，由英国数学家和物理学家阿特武德于1784年制成。实验时将质量同为M(已知量)的重物用绳连接后，放在光滑的轻质滑轮上，处于静止状态。再在一个重物上附加一质量为m的小重物，由于小重物的重力而使系统做初速度为零的缓慢加速运动并测出加速度，完成一次实验后，换用不同质量的小重物，重复实验，测出不同m时系统的加速度。

(1)如图甲左侧物块从静止开始下落，则为了得到图乙，需要直接测量的物理量有___________
A.小重物的质量m
B.大重物质量M
C.绳子的长度
D.重物下落的距离及下落这段距离所用的时间
(2)给过多次重复实验，得到多组a、m数据，作出图象，如图乙所示，已知该图象斜率为k，纵轴截距为b，则可求出当地的重力加速度g=__________，并可求出重物质量M=__________。

许多百岁老人拥有FOXO3基因，科学家猜测，这可能是他们保持身心活跃的关键因素。研究表明，缺乏该基因的小鼠在压力状态下很快出现脑细胞死亡。新的研究发现，这种基因具有使大脑干细胞在压力状态下留存下来的神奇功能。这佐证( )
①意识活动具有一定的物质基础和前提②人的意识是从动物心理发展而来的
③实践是认识的来源和认识发展的动力④从认识到实践，从实践到认识的循环永无止境
A．①②
B．①③
C．②④
D．③④

已知圆的圆心坐标是，半径长是.若直线与圆相切于点，则_____，______.

阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。
The silent killer — air pollution causes seven million premature (过早的) 【1】 (death) a year, not just in 【2】 (develop) countries but also in UK and the USA as well. In China，people are well aware of the health problems it brings.
I check every part every day. If it has heavy air pollution, I will prepare masks for my family. I dislike 【3】 when the air is bad. Because bad air makes it difficult for me to breathe and I think it does influence my 【4】 (perform) at work. A new research in china has also found a link between air quality and levels of intelligence. In the study, 25,000 people living across China 【5】 (test) in language and math skills last year. They found the results of those 【6】 lived in more polluted areas were 【7】 (negative) impacted, especially in languages. It adds to a growing body of evidence that air pollution has an effect not just on the lungs and heart 【8】 on the brain.
This research shows that the longer we are exposed to air pollution, the 【9】 (many) problems we’re storing up for later life. Campaigners hope this study will persuade the British government 【10】 (think) hard before it publishes its clean air strategy next year.

“摘下穷帽子，过上好日子”未来５年，我国将实现７０００多万贫困人口全部脱贫。打嬴这场扶贫攻坚战是（　　　）
①再分配调节机制的主要手段　　 ②全面建成小康社会的目标要求　
③朝共同富裕目标迈进的体现　　　　④转变经济发展方式的主攻方向
A. ①② B. ②③ C. ①③ D. ③④

两个不规则带电导体间的电场线分布如图所示,已知导体附近的电场线均与导体表面垂直,为电场中几个点,并且为紧靠导体表面的两点,选无穷远处为电势零点,则

A. 场强大小关系有
B. 电势大小关系有
C. 将一负电荷放在点时其电势能为负值
D. 将一正电荷由点移到点的过程中电场力做正功

When was the last time you told someone they inspired you to go to work each morning?

Teachers at Oak Park High School in Kansas City, Missouri, did just that this September, when they pulled individual students out of class to tell them just how much they appreciated them.

The students' reactions, which were captured (捕捉) on video and shared on YouTube in a now­viral video, ranged from shy thanks to hugs and tears.

“I have been challenged to find a student who makes me want to come to school every day，” said one teacher in the video, “and that's you.”

“Jamie McSparin, a teacher in charge of the school's academy program for at­risk sophomores (二年级学生) and juniors, posed the challenge，” writes ABC News.

“Initially when we pulled the kids out, they all thought they were in trouble，” McSparin told ABC News. “Any teacher­student interaction always seems to be negative (消极的), and that was something that bothered me, too. No matter if they're a good kid or a troublemaker or anything, they always thought they were in trouble，” she said.

McSparin said she got the idea for the project after attending a professional development workshop this summer called the power of positivity.

“I like the idea of letting students know they are appreciated, because we do appreciate them. I just don't think we say it enough，” she told local news outlet WDAF­TV.

It's safe to say the challenge was effective.

“I feel special，” said one of the boys in the video. “You should，” said his teacher. “You are special.”

篇章导读：本文是一篇新闻报道。文章主要讲述了在美国密苏里州一所校园中所进行的活动——老师让学生们走出教室，告诉学生们，老师很欣赏他们。这一活动的效果是积极有效的。

5．What does the underlined word “posed” in Paragraph 5 mean?

A．Presented.                           B．Rejected.

C．Ignored.                             D．Evaluated.

6．How did the students probably feel when pulled out of the classroom at first?

A．Nervous.                             B．Thrilled.

C．Curious.                             D．Encouraged.

7．What inspired McSparin to challenge the project?

A．The trouble caused by students.

B．The need of shooting the video.

C．A seminar named the power of positivity.

D．A program related to students' interactions.

8．What message does this text mainly convey?

A．Challenge is unavoidable in life.

B．Everyone needs to be appreciated.

C．Positivity outweighs negativity.

D．News media contribute to students' progress.

下列关于基因表达的叙述，正确的是
A. 真核细胞中的RNA都是在细胞核中转录合成的
B. 遗传信息在表达为氨基酸序列的过程中会有损失
C. 翻译时，一种tRNA可能携带多种氨基酸
D. mRNA翻译后只能得到一条多肽链

（地理―选修6：环境保护）阅读材料，回答问题。
降尘，又称“落尘”，是指自然降落于地面的空气颗粒物，其粒径多在10微米以上，计量指标单位为一定时间内、单位面积上地表沉降物质的量。在京津冀及周边地区、长三角地区、汾渭平原三个大气污染防治重点区域2018～2019年秋、冬季大气污染防治攻坚方案中，对城市降尘量提出了明确要求(见下表)。

说明表中不同地区降尘量要求的差异并分析其自然原因。

已知命题为奇函数；命题，则下面结论正确的是
A. 是真命题 B. 是真命题
C. 是假命题 D. 是假命题

补写出下列句子中的空缺部分。
（1）屈原在《离骚》中用“__________，__________”两句写出了当时社会中一些人的行为表现：违背准则，把取悦权贵奉为信条。
（2）李白在《蜀道难》中以感叹结束写蜀道的凶险，进而转入抒写时人事关注的两句是“__________，__________”。
（3）李贺的《雁门太守行》中“__________，__________”两句从声音和色彩两个方面勾勒了一幅肃杀、凝重的战斗图景。

“实现伟大的梦想，必须进行伟大的斗争。强调同一性寓于斗争性之中，并为斗争性所制约。

已知数列的前项和公式为，则数列的通项公式为___．

假定你是学生会主席华。你校将于2019年3月30日举办“大湾区与我”（The Greater Bay Area and Me）英文演讲比赛, 以加强粤港澳姐妹学校间的交流与合作。1l所高中共30位学生将参加全天比赛。请给外教史密斯先生写一封电子邮件, 邀请他当评委并作点评。
注意：
1.词数100左右：
2.可以适当增加细节, 以使行文连贯。
____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

在中，内角、、的对边分别为，，，若，，且，则三角形的面积为__________．

在平面直角坐标系中，曲线的参数方程为（为参数），且曲线上的点对应的参数，以为极点，轴的正半轴为极轴建立极坐标系．
（1）求曲线的普通方程和极坐标方程；
（2）若曲线上的两点满足，过作交于点，求证：点在以为圆心的定圆上.

的展开式中只有第四项的二项式系数最大，则展开式中的系数为_____．

（地理一选修3:旅游地理）
“七河八岛”位于我国江苏省扬州市东北部广陵区，是该市生态自然环境保持最完好的湖泊、平原类型湿地景观。“七河八岛”在功能定位上拟增加水上温泉度假区、古琴研习所、品茗茶园艺等文化景观，下图示意“七河八岛”分布及主要功能区用地结构。

分析挖掘水文化内涵对促进当地旅游业健康发展的作用。