题干

如图表示某种负迁入一个生态系统后,种群增长速率随时间变化的曲线.下列叙述正确的是(    )

A:t1和t2时种群数量相等

B:若t0时种群的数量为N,则t2时其为2N

C:在t0→t2时间内,种群数量呈“S”型增长

D:在t1→t2时间内,该鱼的种群数量呈下降趋势

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答案(点此获取答案解析)

C

同类题2

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    I remember that it was a fall morning when the orchestra teachers came into Miss Newell's third-grade classroom. “You have hands for the viola (中提琴),” Miss Ciano told me. I was excited because my hands were finally good for something. I told my parents I wanted to play, and naturally, they agreed.

    Since I first touched the viola, I haven't been able to put it down. Ignoring the difficulty, I am pulled closer to it each day.

    Classical music is truly my best friend. It is the trusted friend of every man, woman and child. Various feelings are expressed in classical music. I discovered that when I was eleven and played a Bach cello concerto (大提琴协奏曲) in a competition, the first movement was joyful, but the second movement was mysterious and full of pain. From that piece, I learned that music expressed not only feelings, but also sudden mood changes. By listening to classical music, I know that someone else share these feelings. Since I am lucky enough to be able to play classical music, I am comforted when I am upset. It gives me a way to escape from my problems for a short period. Classical music can express my joy, sadness and anger.

    Now look at that fall day and think how gullible I was for believing that anyone, even music teachers, could tell if hands were perfect for a certain instrument. I'm certain they told me I had “viola hands” not because they were fortune-teller, but because there was a lack of violists in our district. Classical music is one of the best things that ever happened to mankind. If you get introduced to it in the right way, it will become your friend for life.

同类题4

阅读下面文言文,按要求回答问题。

【甲】愚公移山(节选)

    太行、王屋二山,方七百里,高万仞。本在冀州之南,河阳之北。

    北山愚公者,年且九十,面山而居。惩山北之塞,出入之迂也,聚室而谋曰:“吾与汝毕力平险,指通豫南,达于汉阴,可乎?”杂然相许。其妻献疑曰:“以君之力,曾不能损魁父之丘,如太行、王屋何?且焉置土石?”杂曰:“投诸渤海之尾,隐土之北。”遂率子孙荷担者三夫,叩石垦壤,箕畚运于渤海之尾。邻人京城氏之孀妻有遗男,始龀,跳往助之。寒暑易节,始一反焉。

【乙】卖蒜老叟

    南阳杨二相公精于拳术,每至演武场传授枪棒,观者如堵。一日,有卖蒜叟,咳嗽不绝声,旁睨而揶揄之。杨大怒,招叟至前,以拳打砖墙,陷入尺许,傲之曰:“叟能如是乎?”叟曰:“君能打墙,不能打人。”杨骂曰:“老奴能受我打乎?打死勿怨!”叟笑曰:“垂死之年,能以一死成君之名,死亦何怨!”老人自缚于树,解衣露腹。杨故取势于十步外,奋拳击之。老人寂然无声,但见杨双膝跪地,叩头曰:“晚生知罪矣。”拔其拳已夹入老人腹中坚不可出。哀求良久,老人鼓腹纵之,已跌出一石桥外矣。老人徐徐负蒜而归,卒不肯告人姓氏。

【注】①睨:眼睛斜着看。②揶揄:出言嘲笑、讽刺。