题干

研究生态系统的能量流动,可以参考如下模型:下列有关叙述正确的是    

A:研究生态系统中的能量流动,一般在群体营养级水平上

B:研究能量流经某一种群的能量时,要考虑到能量被利用和未被利用等方面

C:模型中的“能量输入”就是指捕食者的捕食

D:模型中的“能量散失”指呼吸作用散失的能量

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D

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    Leaving Hanoi on a fiercely hot summer day,after an hour by air,Luang Prabang gradually appears below our airplane wings.From a few hundred meters above,my first impression of this UNESCO-listed heritage(遗产)is an area of green land and mountains,surrounded by snaking rivers.

    Encircled by mountains,the former royal capital of Luang Prabang is more than just the country's picture-perfect showpiece.

    Travelers will be attracted to Luang Prabang by the city's timeless peacefulness with its shiny Buddhist temples, French colonial architecture and friendly people.

    Tourists visiting Luang Prabang shouldn't miss the chance to see one of the most sacred(神圣的)Lao traditions, tak bat,or the Buddhist almsgiving ritual(仪式),which dates back to the 14th century.

    As the sun rises in Luang Prabang,hundreds of Buddhist monks depart from their temples to gather their daily offerings,which most commonly are rice,fresh fruit and traditional sweet snacks.The daily alms gathering begins on the main street before spreading to all the side streets.

    Our group of six got out of our comfy beds at 5 am to join other local residents and tourists to offer alms to the monks.We kneeled by the roadside in front of the 3 Nagas Hotel on the main street with big baskets of steamed sticky rice,waiting quietly until monks of all ages passed by to accept our gifts.

    The daily ritual gives you a wonderful opportunity to experience an ancient Lao tradition.However,there are some strict rules if you wish to join the event.

    Firstly,shoulders,chests and legs must be covered in modest clothing as a mark of respect.You should also remain a suitable distance from the monks.Photographs may be taken,but from a distance and never use a camera flash.The ritual has to be performed in silence.Talking to or touching the monks at any time,even when making an offering,is not allowed.

    Another must-do morning activity is to visit the local market,where you can see the generosity that Mother Nature offers this dreamy land.While walking through the morning market,located within a long and narrow hamlet,I was excited to see all kinds of products from the nearby river and jungle: some ill-fated squirrels lying next to fresh bamboo shoots,different kinds of wild mushrooms and vegetables displayed on banana leaves and giant river catfish in baskets.

    Although Luang Prabang is small,there are many things to see here.Active travelers can get up close and personal with Laos' gentle giants at the elephant conservation camp or take in some scenes of riverside life with a cruise or kayak excursion on the rivers.Two waterfalls that are perfect for picnicking in the foothills nearby,and classes are available in traditional crafts.