The search engines work by means of _________.
A. arranging links to the Internet
B. submitting specific search term
C. updating a knowledge database
D. searching engine spiders
Which of following statements is not true?
A.The writer's mother often killed a mouse by smacking it hard between her hands.
B.The children were not allowed to kill any of the spiders
C.Many of the mice were caught when they tried to eat the cheese in the mousetraps.
D.The family would probably have been happier if the father had not decided to clean out the water tank.
As time went on, hot sun and cool rains made the rock split and break to pieces. Sea waves dashed against the rock. In this way, soil and sand came into being.
Nothing lived on the naked soil. And then the wind and birds brought plant seeds, spiders and other little creatures there. Only plants could grow first. Only they, in sunlight, could produce food from the minerals of the soil, water and air. While many animals landed on the island, they could find no food. A spider spun its web in vain, because there were no insects for its web to catch, In sects couldn' t stay until there were plants for them to eat. So plants had to be the pioneer life on this new island.
The passage centers on ______.
A.how an undersea volcano broke out
B.how an island rose up in the sea
C.how soil was formed on a new island
D.how life began on a volcano-produced island
My mother would never let us kill a spider, not even a hairy old grandfather. "If you want to live and rich," she used to say, "let a spider run alive." And so the spiders, our enemies, were beaten and kicked but never killed. But she had no such dealing with the mice.
One of our problems was that my mother hated cats; and we never owned a single cat. We kept dogs, often two or three at the same time, but very few dogs can move fast enough to catch a lively young mouse. Every night we set a dozen mousetraps(捕鼠器), each with a small piece of cheese. Sometimes the cheese disappeared, but the mice usually seemed too wise to go near the traps. We seldom caught anything.
My mother herself had far better luck. Her arms and hands moved as fast as any cat's paws. Often, when she was scrubbing or polishing a floor on her hands and knees, some foolish little grey fellow would try to run past her. He never got very far. Quick as lightning her hard hands would smack(用掌击) together--and there on the floor would be one dead mouse. "Oh, you were a proud one," she would say to it then.
One day my father decided to clean out the water tank, which stood on four iron legs in a corner upstairs. He was soon sorry that he had started the job. In the mud at the bottom of the tank, there were sixteen of the little grey fellows, all as solid and hard as stones. We had been drinking the water from that tank for twelve years.
Which of followlng statements is true?
A.Because the house was old, the family were troubled by lots of mice and spiders.
B.The children did not live in the house because they were afraid of the spiders.
C.The trouble was that there was no water supply in the old house.
D.Spiders and mice are a part of the family.
若函数f(x)在有限区间(a,b)中有导数,以例子说明之.
反之,若f(x)在有限区间(a, b)中有导数,以例子说明之