题干

如图表示某种兔迁入新环境后种群增长速率随时间变化的曲线.第3年时用标志重捕法调查该兔种群的密度,第一次捕获50只全部标志后释放,一个月后进行第二次捕捉,共捕获未标志的60只,标志的20只.则下列数字最接近K值的是(  )

A:150只 

B:200只 

C:300只    

D:400只

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D

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The Lost Rules of Etiquette

    Etiquette, or good manners, used to be the glue that held society together____Sadly, these days it has mostly gone by the wayside. This list is several best rules of etiquette that have now disappeared.

Opening the Door

    In days gone by, a gentleman would always open doors for ladies____This has now almost entirely disappeared-- and it is pot entirely the fault of the men. I have seen women laugh at men for opening a door for them. They seem to be confusing manners with chauvinism(大男子主义).

Writing Thank-You Notes

    In days gone by, whenever a person received a gift, they would write a thank-you note as soon as possible____Parents would sit children down after a birthday or Christmas and coach them in their first thank-you note. It is a shame that gift giving has now become a virtual obligation and the idea of a thank-you note would be laughed at.
____
         We seem to have completely lost the concept of correct timing when it comes to parties these days____ After all, a party normally has a guest of honor-this is usually the oldest woman present. It was considered extremely rude in the past to leave a party before the guest of honor-and once the guest of honor left, it was a signal to all that they should begin their own preparations to leave.

A. Arriving on Time.

B. Leaving at the Right Time.

C. People leave with various excuses.

D. It enabled people to get on well with each other.

E. This rule was true even if the giver was a relative.

F. It could be the lady they were driving, or a stranger.

G. We've thrown away the concept of a guest of honor at will.