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问题 选择题

北半球高空一架飞机自西向东飞行，飞机的右侧是高压，左侧是低压，下面的叙述正确的是（   ）

A．飞机逆风飞行

B．飞机顺风飞行

C．风从南侧吹来

D．风从北侧吹来

答案

答案：B

题目分析：飞机自西向东飞行，右侧为高压，即高压在南，低压在北，根据水平气压梯度力由高压指向低压，高空的风向与等压线平行，判断高空的盛行风向为西风；故飞机顺风飞行。

点评：本题解题的关键是抓住高空的风的受力作用和风向特征。注意画图分析。

完形填空
配对阅读 左栏是五个中学生遇到的难题，某报专栏编辑给他们的七个建议。请根据五个中学生遇到的难题为他们选出最合适的建议，并将答题卡上对应题目所选的选项涂黑。
小题1:Sometimes I get angry easily and shout at my friends．That makes them think I’m not being friendly to them．
小题2:In my teachers’eyes, I am a good student．Both my classmates and my parents also think so．No one knows what my problem is．I often feel worried about my school work．
小题3:My parents never allow me to play computer games at all．They want me to study all day and do well in my exams．I feel unhappy．
小题4:I want to join in some after-school activities, but my parents think they are too dangerous and don't allow me to go out alone．
小题5:My mother gets me to take piano lessons．She makes it a rule that I must practice two hours a day．I really try my best, but I just can't play well．
A．Let your parents know you will not be alone．Also, you can ask a teacher to talk to your parents about the after-school activities．
B．Don't worry．You can still have some indoor sports．
They are also fun．
C．Don't worry, even great piano players have to practice. Hard work and a lot of practice are the only ways to become a good piano player．
D．When you feel angry you should stop talking and count to ten or walk away until you keep quiet．
E．Tell your friends how you are feeling．You are in a
new class, so you still need their friendship．Also, you can make new friends．
F．Don't worry．Everybody worries about their school
work, even those students like you who study well.　Find a hobby or a sport to help you relax for a while．
G．Tell your parents that many kids play computer games and do well at school, too．Ask them to let you play computer games for a short time on weekends．
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单项选择题

下列关于花粉和胚囊败育原因的叙述正确的是（）

A.多倍体品种或单倍体品种常常花粉或胚囊败育

B.胚囊败育与营养足不足无关

C.栽培技术常导致花粉败育

D.与花粉及胚囊形成过程中的环境条件关系不大
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