We can infer from the passage that one benefit of fluoride to healthy teeth is                                .
A.It strengthens tooth enamel 
B.It stimulates saliva production
C.It makes teeth whiter        
D.It is a replacement for brushing and flossing in dental care

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IV. Fill in each numbered blank with one suitable word or phrase.
Water polo is a rapidly growing sport in the United States and internationally as (31) ______. For anyone involved in playing or being a spectator, it is important to understand the rules of the game.
Each team (32) ______ of one goalie and six field players. Each field player plays both offense and defense, and the goalie is not allowed on the other half of the pool. There are many different arrangements of players in front of the goal. The (33) ______ of the players depends on the play that is being run, similar to basketball or hockey.
One important rule is that the ball can only be handled by one hand at a time. If a player (34) ______ the ball, which is the size of a volley ball, yellow and with rubber grip, with both hands, the referee calls a turnover and the possession of the ball goes to the opposing team.
The playing time, (35) ______ on the rules of play and the level of competition. Usually, men play four 7-minute quarters while women play four 6-minute quarters. Teams are usually allowed 2 time outs per game, but this may vary. (36) ______ consist of swimsuits for both men and women, as well as a cap on the head with plastic ear protectors and the player's number on both sides. Visiting teams wear lighter color caps, while home wears the darker color. In (37) ______, one point is given for each time the ball is thrown into the goal, and in some leagues there is a 2-point line several meters out of the goal. Each quarter begins with a (38) ______ in which the fastest members of each team race toward the ball, which is placed at the halfway point on the water by the referee.
Water polo is an (39) ______, challenging, and fun sport. It is full contact and its competitiveness cannot be underestimatted. The game is great to watch and (40) ______ better to play. You may not imagine what goes on underwater that no one, especially not the referee, can see. Water polo is a growing sport for good reason, and it may soon be one of the leading sports for both men and women's athletics.
(31) 
A.well                                    
B.too                          
C.so                            
D.also

Read the following passage, and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
Alexis de Tocqueville, the French political scientist, historian, philosopher and politician, is most famous for a four-volume book he wrote called “Democracy in America”. He came to America in 1831 to study the American form of democracy and what it might mean to the rest of the world. After a visit of only nine months, he wrote a remarkable book which is regarded as a classic. De Tocqueville had unusual powers of observation. He described not only the democratic system of government and how it operated, but also its effect on how Americans think, feel, and act. Many scholars believe he had a deeper understanding of traditional American beliefs and values than anyone else who has written about the United States. What is so remarkable is that many of these traits which he observed nearly 200 years ago, are still visible and meaningful today. His observations are also important because the timing of his visit, the 1830s, was before America was industrialized. This was the era of the small farmer, the small businessman, and the settling of the western frontier. It was the period of history when the traditional values of the new country were newly established. In just a generation, some 40 years since the adoption of the U.S. Constitution, the new form of government had already produced a society of people with unique values. He was, however, a neutral observer and saw both the good and bad sides of these qualities.
The first part of “Democracy in America” was written in 1831-32 and published in 1835. A highly positive and optimistic account of American government and society, the book was very well received. He attempted to get a glimpse of the essence of American society, all the while promoting his own philosophy: the equaling of the classes and the inevitable depth of aristocratic privilege. The rest of the book he labored on for four years, and in 1840 the second part was published. This was substantially more pessimistic than the first, warning of the dangers despotism and governmental centralization, and applying his ideas and criticisms more directly to France. As a result, it was not received as well as the first part, except in England where it was acclaimed highly.
The word “unique” in the passage is closest in meaning to
A.clearly identifiable 
B.outstanding      
C.unmatched      
D.positive