2014浙江杭州二中第五次月考（3月）英语试题答案(3)

Tom went on whitewashing. He did not look at Ben. Ben stared a moment and then said: “Hello! I’m going swimming, but you can’t go, can you?”
No answer. Tom moved his brush carefully along the fence and looked at the result with the eye of an artist. Ben came nearer. Tom’s mouth watered for the apple, but he kept on working.
Ben said, “Hello, old fellow, you’ve got to work, hey?”
Tom turned suddenly and said, “Why, it’s you, Ben! I wasn’t noticing.”
“Say —I’m going swimming. Don’t you wish you could? But of course you’d rather work — wouldn’t you? Of course you would.”
Tom looked at the boy a bit, and said “What do you call work?”
“Why, isn’t that work?”  Tom went back to his whitewashing, and answered carelessly.
“Well, maybe it is, and maybe it isn’t. All I know is, it suits Tom Sawyer.”
“Oh come, now, you don’t mean to say that you like it?”  The brush continued to move.
“Like it? Well, I don’t see why I shouldn’t like it. Does a boy get a chance to whitewash a fence every day?”
Ben stopped eating his apple. Tom moved his brush back and forth, stepped back to look at the result, added a touch here and there, and stepped back again. Ben watched every move and got more and more interested. Soon he said,
“Say, Tom, let me whitewash a little.” 
Tom thought for a moment, was about to agree; but he changed his mind.
“No —no —it won’t do, Ben. You see, Aunt Polly wants this fence to be perfect. It has got to be done very carefully. I don’t think there is one boy in a thousand, maybe two thousand, that can do it well enough.”
“No —is that so? Oh come, now —let me just try. Only just a little.” “Ben, I’d like to, but if it isn’t done right, I’m afraid Aunt Polly … ”
“Oh, I’ll be careful. Now let me try. Say —I’ll give you the core of  my apple.”
“Well, here —No, Ben, now don’t. I’m afraid …”
“I’ll give you all of it.”
Tom gave up the brush with unwillingness on his face, but joy in his heart. And while Ben worked at the fence in the hot sun, Tom sat under a tree, eating the apple, and planning how to get more help. There were enough boys. Each one came to laugh, but remained to whitewash. By the time Ben was tired, Tom sold the next chance to Billy for a kite; and when Billy was tired, Johnny bought in for a dead rat —and so on, hour after hour. And when the middle of the afternoon came, Tom had won many treasures.
And he had not worked. He had had a nice idle time all the time, with plenty of company －and the fence had been whitewashed three times. If he hadn’t run out of whitewash, Tom would have owned everything belonging to his friends.
He had discovered a great law of human action, namely, that in order to make a man or a boy want a thing, it is only necessary to make the thing difficult to get. 
44. Why did Tom take all his bits of toys out of his pockets?
A. Because he is tired and wanted to play with his toys.
B. Because he wanted to throw his toys away.
C. Because he wanted to give his toys to his friends. 
D. Because he wanted to know if he could buy help with his toys.
45. Tom was about to agree to let Ben whitewash when he changed his mind because ____________.
A. Tom wanted to do the whitewashing by himself
B. Tom planned to make Ben give up his apple first
C. Tom was unwilling to let Ben do the whitewashing
D. Tom was afraid Ben would do the whitewashing better.
46. What made Ben Rogers eagerly gave up his apple and offer to brush the fence for Tom?
   A. His warm heart and kindness to friends. B. His curiosity about Tom’s brushing job.
   C. Tom’s threat. D. Aunt Polly’s idea.
47. Which of the following is the most suitable title for this passage?
A. The Happy Whitewasher  B. Tom And His Fellows
C. Whitewashing A Fence   D. How To Make The Things Difficult To Get
                                       C
Can people change their skin color without suffering like pop king Michael Jackson? Perhaps yes. Scientists have found the gene that determines skin color.
    The gene comes in two versions, one of which is found in 99 percent of Europeans. The other is found in 93 to 100 percent of Africans, researchers at Pennsylvania State University report in the latest issue of Science.
    Scientists have changed the color of a dark-striped zebra-fish（斑马鱼） to uniform gold by inserting a version of the pigment (色素) gene into a young fish. As with humans, zebra-fish skin color is determined by pigment cells, which contain melanin (黑色素). The number, size and darkness of melanin per pigment cell determine skin color.
    It appears that, like the golden zebra-fish, light-skinned Europeans also have a mutation (变异) in the gene for melanin production. This results in less pigmented skin.
    However, Keith Cheng, leader of the research team, points out that the mutation is different in human and zebra-fish genes.
    Humans acquired dark skin in Africa about 1.5 million years ago to protect bodies from ultra-violet rays of the sun (太阳光紫外线), which can cause skin cancer.
    But when modern humans leave Africa to live in northern latitudes, they need more sunlight on their skin to produce vitamin D. So the related gene changes, according to Cheng.
    Asians have the same version of the gene as Africans, so they probably acquired their light skin through the action of some other gene that affects skin color, said Cheng.