题干

热机的效率较低,为了提高热机的效率,你认为下列方法目前不可能的是(   )

A:尽量使燃料充分燃烧

B:尽量减少各种热损失

C:尽量减少因克服摩擦力而额外消耗的能量

D:想办法把燃料放出的热量全部用来做有用功

上一题 下一题 0.0难度 选择题 更新时间:2014-06-23 01:47:54

答案(点此获取答案解析)

D

同类题1

阅读下文,回答问题

驿路梨花(节选)

    我们正在劳动,突然梨树丛中闪出了一群哈尼小姑娘。走在前边的约莫十四五岁,红润的脸上有两道弯弯的修长的眉毛和一对晶莹的大眼睛。我想:“她一定是梨花。”

    瑶族老人立即走到她们面前,深深弯下腰去,行了个大礼,吓得小姑娘们像小雀似的蹦开了,接着就哈哈大笑起来:“老爷爷,你给我们行这样大的礼,不怕折损我们吗”?

    老人严肃地说:“我感谢你们盖了这间小草房。”

    为头的那个小姑娘赶紧摇手:“不要谢我们!不要谢我们!房子是解放军叔叔盖的。”

    接着,小姑娘向我们讲述了房子的来历。十多年前,有一队解放军路过这里,在树林里过夜,半夜淋了大雨。他们想,这里要有一间给过路人避风雨的小屋就好了,第二天早上就砍树割草盖起了房子。她姐姐恰好过这边山上来拾菌子,好奇地问解放军叔叔;“你们要在还里长住?”解放军说:“不,我们是为了方便过路人。是雷锋同志教我们这样做的。“她姐姐很受感动。从那以后,常常趁砍树、拾菌子、找草药的机会来照料这小茅屋。

    原来她还不是梨花。我问:“梨花呢?”

    “前几年出嫁到山那边了。”

    不用说,姐姐出嫁后,是小姑娘接过任务,常来照管这小茅屋。

    我望着这群充满朝气的哈尼小姑娘和那洁白的梨花,不由得想起了一句诗:“驿路梨花处开”。

同类题3

根据短文理解,选择正确答案。

    Some 30,000 years ago, artists who lived in caves in Europe painted pictures of the animals around them: panthers, hyenas, rhinos, cave lions, mammoths and other creatures which have been extinct for a long time. The paintings were highly realistic. Some even showed movement.

    The artwork, more than a thousand drawings, is considered the oldest group of human cave drawings which have ever been discovered. They were preserved because the cave was sealed---closed off--for more or less 23,000 years.

    Fast forward to December 18, 1994, a group of French cave scientists were exploring caves in southern France. Jean Marie Chauvet, who led the group then, describes the process of discovering the cave paintings. “At that time I was in the front, Eliette just walked behind me, Christian behind. Eliette said she saw two marks with red ochre and she said, ‘They came here.' And at this very moment everything began. The drawings and everything linked to the parietal art(壁画). That is where it is tarted.”

    Cave art expert Jean Clotttes reviewed the paintings. “I was amazed at the number of paintings there were and paintings of their quality and particularly in front of the panel of the horses.”

    Scientific analysis confirmed the prehistoric date of the artwork. Studies showed the drawings were created tens of thousands of years ago, before human history was written. The United Nations' cultural agency UNESCO lists the cave as a World Heritage Site. They say that the drawings form a remarkable expression of early human artistic creation of grand excellence and variety.

    The Chauvet Cave has been named after the explorer who first entered it. However, its environment and drawings are too fragile to be visited by human beings. So the cave is closed, and only people there for scientific purposes can go inside and see the artwork.

    However, French authorities asked experts to create an exact copy of the cave, called Pont d'Arc Cavern. The copy, which we also called replica, cost more than 59 million dollars to build. It opened at the end of April in France.

    Pascal Terrasse is the president of the cavern. He says everyone will be able to experience the thrill of looking at drawings made by the first humans in Europe. He says the place is magic because it is done so well. Authorities say they think as many as 400,000 people will be allowed to visit Pont d'Arc Cavern every year.