问题 选择题

下列说法错误的是(  )

A.二次函数y=-2x2中,当x=0时,y有最大值是0

B.二次函数y=4x2中,当x>0时,y随x的增大而增大

C.在三条抛物线y=2x2,y=-0.5x2,y=-x2中,y=2x2的图象开口最大,y=-x2的图象开口最小

D.不论a是正数还是负数,抛物线y=ax2(a≠0)的顶点一定是坐标原点

答案

A、a=-2<0,抛物线开口向下,当x=0时,y有最大值是0,正确;

B、二次函数y=4x2中,当x>0时,y随x的增大而增大,正确;

C、因为|2|>|-1|>|-0.5|,所以,y=2x2的图象开口最小,y=-0.5x2的图象开口最大,错误;

D、不论a是正数还是负数,抛物线y=ax2(a≠0)的顶点一定是坐标原点,正确.

故选C.

阅读理解

阅读理解

     "Our aim is to take our art to the world and make people understand what it is to move," said David

Belle, the founder of parkour(跑酷).

     Do you love running? It is a good exercise, yet many people find it boring. But what if making your

morning jog a creative one? Like jumping from walls and over gaps, and ground rolls? Just like the James Bond in the movie Casino Royale? Bond jumps down from a roof to a windowsill and then runs several

blocks over obstacles on the way. It is just because of Bond's wonderful performances that the sport has

become popular worldwide.

     Yes, that's parkour, an extreme street sport aimed at moving from one point to another as quickly as

possible, getting over all the obstacles in the path using only the abilities of the human body. Parkour is

considered an extreme sport. As its participants dash around a city, they may jump over fences, run up

walls and even move from rooftop to rooftop.

Parkour can be just as exciting and charming as it sounds, but its participants see parkour much more

than that.

     Overcoming all the obstacles on the course and in life is part of the philosophy(理念) behind parkour. This is the same as life. You must determine your destination, go straight, jump over all the barriers as if

in parkour and never fall back from them in your life, to reach the destination successfully. A parkour

lover said, "I love parkour because its philosophy has become my life, my way to do everything."

     Another philosophy we've learnt from parkour is freedom. It can be done by anyone, at any time,

anywhere in the world. It is a kind of expression of trust in yourself that you earn energy and confidence.

1. Parkour has become popular throughout the world because of _____.

A. its founder, David Belle

B. the film, Casino Royale

C. its risks and tricks

D. the varieties of participants

2. The underlined word "obstacles" in Paragraph 2 is closest in meaning to "_____".

A. streetsB. objects

C. barriersD. roofs

3. Which of the following is true of parkour?

A. It challenges human abilities.

B. It is a good but boring sport.

C. It needs special training.

D. It is a team sport.

4. As its participants move around a city, _____.

A. they can ask for help

B. they may choose to escape

C. they should run to extremes

D. they must learn to

单项选择题 A1/A2型题