磺甲基化聚丙烯酰胺是一种性能良好的高温降滤失剂，其代号是（）。A、HPH B、HPH

C

Few laws are so effective that you can see results just days after they take effect. But in the nine days since the federal cigarette tax more than doubled—to $1. 01 per pack—smokers have jammed telephone “quit lines” across the country seeking to kick the habit.

This is not a surprise to public health advocates（拥护者） They’ve studied the effect of state tax increases for years, finding that smokers, especially teens, are price sensitive. Nor is it a shock to the industry, which fiercely fights every tax increase.

The only wonder is that so many states insist on closing their ears to the message. Tobacco taxes improve public health, they raise money and most particularly, they deter people from taking up the habit as teens, which is when nearly all smokers are addicted. Yet the rate of taxation varies widely.

In Manhattan, for instance, which has the highest tax in the nation, a pack of Marlboro Light Kings cost ＄10.06 at one drugstore Wednesday. In Charleston, S. C., where the 7-cent-a-pack tax is the lowest in the nation, the price was $4. 78.

The influence is obvious.

In New York, high school smoking hit a new low in the latest surveys—13.8%, far below the national average. By comparison, 26% of high school students smoke in Kentucky, other low-tax states have similarly depressing teen-smoking records.

Hal Rogers, Representative from Kentucky, like those who are against high tobacco taxes, argues that the burden of the tax falls on low-income Americans “who choose to smoke.”

That’s true. But there is more reason in keeping future generations of low-income workers from getting hooked in the first place. As for today’s adults, if the new tax drives them to quit, they will have more to spend on their families, cut their risk of cancer and heart disease and feel better.

49. The text is mainly about ________.

A. the price of cigarettes                     B. the rate of teen smoking

C. the effect of tobacco tax increase            D. the differences in tobacco tax rate

50. The underlined word "deter” in Paragraph 3 most probably means ________.

A. discourage        B. remove            C. benefit            D. free 

51. Rogers’ attitude towards the low-income smokers might be that of ________.

A. tolerance          B. unconcern          C. doubt             D. sympathy

52. What can we learn from the last paragraph?

A. The new tax will be beneficial in the long run.

B. Low-income Americans are more likely to fall ill.

C. Future generations will be hooked on smoking.

D. Adults will depend more on their families.

设有关系R(S，D，M)，其函数依赖集F＝S→D，D→M。则关系R至多满足( )。

A．1NF
B．2NF
C．3NF
D．BCNF

磷酸氢二胺(纯)

绝对高程通常称为（），用“H”表示。

事务T1，T2，T3分别对数据D1，D2，D3并发操作如下图所示，其中T1与T2间的并发操作存在的问题是 (1) 。T2与T3间的并发操作存在的问题是 (2) 。