玩“过山车”是一项非常惊险刺激的娱乐活动.如图所示,过山车时而从轨道的最低点D上

题型:选择题

问题:

玩“过山车”是一项非常惊险刺激的娱乐活动.如图所示,过山车时而从轨道的最低点D上升到最高点A,时而从最高点A飞驰而下。过山车在运动过程中,若不计能量损失,只有动能和势能的相互转化。下列说法正确的是

[ ]

A.A点机械能小于B点机械能      

B.D点动能最大,A点势能最大  

C.D点动能最大,A点机械能最大    

D.A点势能最大,机械能最大

考点:机械能转化与守恒
题型:选择题
列式计算.
(1)一个数比它的60%多12.8,求这个数.
(2)比的两个外项是2与x,两个内项是
1
20
与8.
题型:选择题

在关系模式中,如果属性A和B存在1对1的联系,则说( )。

A.A→B
B.B→A
C.A←→B
D.以上都不是

题型:选择题

食管穿孔的影像学征象包括()。

A.尖刺状突

B.龛影形成

C.管扭曲成角

D.憩室样变

E.纵隔炎

题型:选择题

网络商品中介交易的流程包括()

A、买卖双方根据网络商品交易中心提供的信息,选择自己的贸易伙伴

B、网络商品交易中心从中撮合,促使买卖双方签订合同

C、配送部门送货给买方

D、配送部门到卖方取货

题型:选择题

Most people have no idea of the hard work and worry that gointothe collecting of those fascinating birds and animals that they pay to see in the zoo.One of the questions that is always asked of me is 1 I became an animal collector in the first 2.The answer is that I have always been interested in animals and zoos.According to my parents, the first word I was able to say with any 3 was not the conventional “mamma” or “daddy”,4 the word “zoo”, which I would 5 over and over again with a shrill 6 until someone, ingroupsto 7 me up, would take me to the zoo.When I 8 a little older, we lived in Greece and I had a great 9 of pets, ranging from owls to seahorses, and I spent all my spare time 10 the countryside in search of fresh specimens to 11 to my collection of pets.12 on I went for a year to the City Zoo, as a student 13 , to get experience of the large animals, such as lions, bears, bison and ostriches,14 were not easy to keep at home.When I left, I 15 had enough money of my own to be able to 16 my first trip and I have been going 17 ever since then.Though a collector's job is not an easy one and is full of 18 ,it is certainly a job which will appeal 19 all those who love animals and 20.

请在2处填上正确答案()

A.region

B.field

C.place

D.case

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