在过去的几个世纪中,古生物学家用化石标本间的细微差异把特思莱特普斯分为16类。但是这种划分并不正确。因为用来区分的样本中,有11类的标本都是来自生活在同一地区同一时代的动物。 下面哪个如果正确,能使以上观点的结论正确地得出
A. 并不是每一种生活在指定地区的动物都会作为化石被保存下来。
B. 特思莱特普斯的每个真正种类中,至少会有一个个体被发现作为化石标本。
C. 没有一个地理区域在同一时代会有超过三种相似的种类居住。
D. 许多种类的个体之间显示出了很大的差异性。
E. 来自不同地区的特思莱特普斯化石标本之间的差别与来自相同地区的特思莱特普斯化石标本之间的差别同样明显。
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There are many kinds of ants in America. One kind is very strong. People are afraid of it, and animals are afraid of it, too. These ants move in large groups. They eat all the animals on their way. They can kill and eat elephants, anti they can eat wood houses. Sometimes even people are killed by them. When the ants come near, people leave their homes. But people are sometimes glad after the ants pass, because they can see no insects (昆虫) or snakes. The strong ants move ______ .
A. alone
B. in large groups
C. at night
This is my room. Near the window there is a desk. I often do my homework at it. You can see some books, some flowers in a vase, a ruler and a pen. On the wall near the desk there is a picture of a cat. There is a clock above the end of my bed. I usually put my football under my bed. Of course there is a chair in front of the desk. I sit there and I can see the trees and roads outside. What’s in the picture
A ruler.
B. A clock.
C. A cat.
I am in a bus on a rainy day, and a woman with a dog gets on the bus. It is a big dog and its feet are not clean. I don’t want the dog to sit near me. But the woman says to the conductor, "Oh, I pay for my dog. Can he sit here like the other people" The conductor looks at the dog and says, "Yes, madam. But like the other people, he must not put his feet on the chair.\ The conductor allows the dog to sit on the chair.
A. [A] True.
B. False.
设曲线y=x2-1在点(x0,y0)处的切线l与直线y=2x+1平行, 求切线l的方程。