问题 单项选择题

一个牙齿健康的15岁儿童,如果由饮水氟浓度为0.4mg/L地区迁至浓度为2.0mg/L地区,其氟牙症发生的可能性为()

A.0

B.25%

C.50%

D.75%

E.100%

答案

参考答案:A

解析:患氟牙症牙数的多少取决于牙发育矿化的时期在高氟区生活时间的长短,出生至出生后在高氟区居住多年,可使全口牙受侵袭;如2岁前生活在高氟区,以后迁移至非高氟区,在恒牙氟斑牙可表现在前牙和第一恒磨牙;如果6~7岁以后再迁入高氟区,则不出现氟斑牙。因此其氟牙症发生的可能性为0。

阅读理解

 根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项是多余的。  

Shopping is not as simple as you may think! There are all sorts of tricks at play each time we reach out for that particular brand of product on the shelf.

  1 . Health foods are packaged in greens, yellows or browns because we think of these as healthy colors. Ice cream packers are often blue and expensive goods, like chocolates, are gold or silver.

  2 . Recently, some kind of pain killer was brought out, but researchers found it didn’t sell well, because the color made the product look weak and ineffective. Eventually, it came on the market in a dark blue and white package -- because we think of blue as safe, and white as calm.

 3 . But quite often a bottle doesn’t contain as much as it appears to.

It is believed that the better-known companies spend, on average, 70 percent of the total cost of the product itself on packaging!

The most successful producers know the troth:   4 . The founder of Pears soup, who for 25 years has used pretty little girls to promote their goods, came to the conclusion: “  5 .”

A.It’s not enough to have a good product.

B.Coloring, for example, varies according to what the producers are trying to sell.

C.Any fool can make soup, but it takes a genius to sell it.

D.The colors tricked the customers into shopping.E. The size of a product can attract a shopper.

F. A good product is an advantage.

G. The colors turned the customers off.

问答题 简答题