关于生物多样性的保护，正确的是[ ] A．自然保护区的功能是接纳各地迁移和捕来的

During the past 15 years, the most important component of executive pay packages, and the one .most responsible for the large increase in the level of such compensation, has been stock-option grants. The increased use of option grants was justified as a way to align executives’ interests with shareholders’. For various tax, accounting, and regulatory reasons, stock-option grants have largely comprised "at-the-money options": rights to purchase shares at an "exercise price" equal to the company’s stock price on the grant date. In such at-the-money options, the selection of the grant date for awarding options determines the options’ exercise price and thus can have a significant effect on their value.
Earlier research by financial economists on backdating practices focused on the extent to which the company’s stock price went up abnormally after the grant date, My colleagues and I focused instead on how a grant-date’s price ranked in the distribution of stock prices during the month of the grant. Studying the universe of about 19,000 at-the-money, unscheduled grants awarded to public companies’ CEOs during the decade 1996-2005, we found a clear relation between the likelihood of a day’s being selected as a grant date for awarding options, and the rank of the day’s stock price within the price distribution of the month: a day was most likely to be chosen if the stock price was at the lowest level of the month, second most likely to be chosen if the price was at the second-lowest level, and so forth. There is an especially large incidence of "lucky grants" (defined as grants awarded on days on which the stock price was at the lowest level of the month): 12 percent of all CEO option grants were lucky grants, while only 4 percent were awarded at the highest price of the month.
The passage of the Sarbanes-Oxley Act in August 2002 required firms to report grants within two days of any award. Most firms complied with this requirement, but more than 20 percent of grants continued to be reported after a long delay. Thus, the legislation could be expected to reduce but not eliminate backdating. The patterns of CEO luck are consistent with this expectation: the percentage of grants that were lucky was a high 15 percent before enactment of the law, and declined to a lower, but still abnormally high, level of 8 percent afterwards.
Altogether, we estimate that about 1,150 CEO stock-option grants owed their financially advantageous status to opportunistic timing rather than to mere luck. This practice was spread over a significant number of CEOs and firms: we estimate that about 850 CEOs ( about 10 percent) and about 720 firms ( about 12 percent) received or provided such lucky grants. In addition, we estimate that about 550 additional grants at the second-lowest or third-lowest price of the month owed their status to opportunistic timing.
The cases that have come under scrutiny thus far have led to a widespread impression that opportunistic timing has been primarily concentrated in "new economy" firms. But while the frequency of lucky grants has been somewhat higher in such firms, more than 80 percent of the opportunistically timed grants have been awarded in other sectors. Indeed, there is a significantly higher-than-normal incidence of lucky grants in each of the economy’s 12 industries.

The main purpose of the author’s study is to find out

A．how the company’s stock price went up after the grant date.

B．how stock price distribution influence the rank of granted price.

C．how backdating practices influence the value of stock shares.

D．how the granted price ranked in the month of the grant.

在队列研究中，人年数的计算可采用下列哪些方法？（）

A.对于固定人群，每一成员的观察年数是从观察开始直至终点事件出现或研究结束

B.对于固定人群，总的观察人年数是每一成员的具体观察年数的总和

C.对于小样本动，态人群，亦可将每一，成员的具体观察时间相加

D.对于大样本动态人群，其总人时数等于观察人数乘以总的观察时间

E.对于动态人群，当年加入或退出的均可按1/2人年计算

我国目前水污染非常严重。据1986年统计，全国废水排放量为339亿多吨，比1980年增加26亿吨，其中工业废水260亿吨，比1980年增加了26亿吨，每万元产值工业废水排放量为377吨，工业废水占废水总量的77％。这些排放的废水大部分未经处理直接排入江、河、湖、海，使城市附近的水域90％受到不同程度的污染。据有关部门对我国5．5万千米河段的调查，结果表明，我国多数河段的水质不符合标准，有85．9％的水不符合饮用、渔业用水标准，有23．7％的不符合农田灌溉用水标准。

1986年，我国每百万元产值工业废水排放量为（）。

A．377吨

B．3770吨

C．37．7万吨

D．3．77万吨

下列哪一项不是表寒证的临床表现()

A.恶寒发热

B.头身疼痛

C.鼻流清涕

D.咽喉肿痛

E.无汗

导线网中至少要有（）个结点。

A、0个

B、1个

C、2个

D、3个