未解之谜 unsolved ____.

Lack of preparation and unsolved cultural problems will not make the performance lower.

He soon realized that it was a tricky thing to sell out all the overstocked goods. A: confusing B: unsolved C: dishonest D: difficult

Why are patients with speech disorders able to think without having adequate control of language A: They use different concepts. B: They do not think linguistically. C: It still remains an unsolved mystery. D: Thinking is independent of language.

3.5Entrepreneurs need to position themselves for entrepreneurial choices in order to: A: focus on entrepreneurial projects that meet their own characteristics B: find entrepreneurial opportunities in line with development trends C: discover unsolved problems D: fill gaps in the market

In the second paragraph, the author gives two examples of social problems to show that ______. A: social problems are on the rise currently B: the government does not try hard to solve such problems C: some attacks on such problems are often blind D: such problems often go unsolved

The idea that engineers need to create a new design to solve every problem is obsolete because __________. A: you can firstly browse the Internet or other information system to see if somebody else has already designed something is close to what you need B: you may discover somebody already has manufacturing drawings, numerical control programs, and everything else required to manufacture your product. C: you can focus your professional competence on unsolved problems D: All of the above answers.

Passage 1 Left-handers and Right-handers Imagine you are a left-hander. Suddenly everything in the world is changed. The door locks are on the wrong side of doors. The shift-gears in your car is in the wrong place. Handles on tin openers are on the wrong side and turn the wrong way. Twenty-five million Americans wake up every day in just such a sorry situation. They are one in ten of us who are left-handed and must face the world designed for the right-handed majority. Why we are left or right-handed remains one of the greatest unsolved mysteries of science. We know that nearly two out of three lefties are men and that left-handedness runs in families. According to one study almost half of the children of two left-handed parents will be left-handed. The Scots-Irish family Kerr produced so many left-handers that in 1470 the family built its house stairway with a reverse twist. On the other hand, heredity alone cannot explain lefties. 84 percent of them are born of two right-handed parents. And in 12 percent of twins, one will be right-handed, the other left. Perhaps the greatest puzzle of all is not why some people are left-handed, but rather why so few are. In fact, almost equal numbers of individuals will favor either the right or the left. However, scientists are trying to set things right and they are beginning to study the many ways left-handers differ from right-handers by considering how their brains work. 1. Based on the passage, we know that of Americans are left-handers. A) 25% B) 10% C) 16% D) 12% 2. We can say from the passage that . A) scientists have found out how left-handers' brains work B) people prefer to be right-handers C) left-handers lead a life in somewhat inconvenient way D) no other families have so many left-handers as the Kerrs 3. Which of the following statements is true according to the passage? A) Half of the left-handers are men. B) Most of the twins are left-handers. C) There are more male left-handers than female ones. D) The greater part of left-handers have left-handed parents 4. Why so few people are left-handers . A) has nothing to do with heredity B) is not known by scientists C) puzzles left-handed people D) is no concern of common people 5. The word "reverse" (Last Line, Para.3) most probably means . A) contrary B) different C) ridiculous D) mysterious New Words and Expressions heredity 遗传 twist 弯曲，曲折处