题干

下列命题:①在ABC中,若A>B,则sinA>sinB;②已知AB=3,4,CD=-2,-1,则ABCD上的投影为-2;③已知P:xR,cosx=1q:xR,x2-x+1>0,则“p¬q”为假命题.其中真命题的个数为( )

A:0

B:1

C:2

D:3

上一题 下一题 0.0难度 选择题 更新时间:2019-04-18 07:37:31

答案(点此获取答案解析)

C

同类题4

阅读短文回答问题

    我爱鸟。

    从前我常见提笼架鸟的人,清早在街上溜达(现在这样有闲的人少了)。我感觉兴味的不是那人的悠闲,却是那鸟的苦闷。胳膊上架着的鹰,有时头上蒙着一块皮子,羽翮不整地蜷伏着不动,哪里有半点儿瞵视昂藏的神气?笼子里的鸟更不用说,常年地关在栅栏里,饮啄倒是方便,冬天还有遮风的棉罩,十分地“优待”,但是如果想要“抟扶摇而直上”,便要撞头碰壁。鸟到了这种地步,我想它的苦闷,大概是仅次于粘在胶纸上的苍蝇;它的快乐,大概是仅优于在标本室里住着吧?

    我开始欣赏鸟,是在四川。黎明时,窗外是一片鸟啭,不是吱吱喳喳的麻雀,不是呱呱噪啼的乌鸦,那一片声音是清脆的,是嘹亮的。有的一声长叫,包括着六七个音阶;有的只是一个声音,圆润而不觉其单调;有时是独奏,有时是合唱:简直是一派和谐的交响乐。不知有多少个春天的早晨,这样的鸟声把我从梦境唤起。等到旭日高升,市声鼎沸,鸟就沉默了,不知到哪里去了。一直等到夜晚,才又听到杜鹃叫,由远叫到近,由近叫到远,一声急似一声,竟是凄绝的哀乐。客夜闻此,说不出的酸楚!   

    在白昼,听不到鸟鸣,但是看得见鸟的形体。世界上的生物,没有比鸟更俊俏的。多少样不知名的小鸟,在枝头跳跃。有的曳着长长的尾巴,有的翘着尖尖的长喙,有的是胸襟上带着一块照眼的颜色,有的是飞起来的时候才闪露一下斑斓的花彩。几乎没有例外的,鸟的身躯都是玲珑饱满的,细瘦而不干瘪,丰腴而不臃肿,真是减一分则太瘦,增一分则太肥,那样的秾纤合度。跳荡得那样轻灵,脚上像是有弹簧。看它高踞枝头,临风顾盼——好锐利的喜悦刺上我的心头。不知是什么东西惊动它了,它倏地振翅飞去,它不回顾,它不悲哀,它像虹似的一下就消逝了,它留下的是无限的迷惘。有时候稻田里伫立着一只白鹭,拳着一条腿,缩着颈子;有时候“一行白鹭上青天”,背后还衬着黛青的山色和釉绿的梯田。就是抓小鸡的鸢鹰,啾啾地叫着,在天空盘旋,也有令人喜悦的一种雄姿。

同类题5

阅读短文,下列问题

 B

    Each year there is an increasing number of cars on the roads and streets as millions of new cars and trucks are produced. One out of every six Americans works at putting together the parts of the cars, driving trucks, building roads, or filling cars with gas. Americans won't live without cars!

    Most Americans would find it hard to think what life could look like without a car.However,some have realized the serious problem of the air pollution caused by the car. The polluted air becomes poisonous and dangerous to people's health.

    One way to get rid of the polluted car is to design a car that does not pollute.That's what several of the large car factories have been trying to do. But to build a clean car is easier said than done. Progress in this field has been slow.

    Another way is to take the place of the car engine (发动机)by something else. Inventors are now working on steam cars as well as electric cars. Many makers believe that it will take years to develop a practical model that pleases man.

    To prevent the world from being polluted by car, we'll have to make some changes.Americans,for example, have to cut down on the number of their total cars. They are encouraged to travel and to go to work by bicycle. Bicycling is thought to help keep the air clean.

    But this change doesn't come easily—a large number of workers may find themselves without jobs if a car factory closes down. Thus the problem of air pollution would become less important than that of unemployment.

    Althoughcars have led us to a better life, they have also brought us new problems.