首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________sort—conve
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________sort—conve
admin
2022-01-04
32
问题
Sunlight is free, but that is no reason to waste it. Yet even the best silicon solar cells—by far the most【C1】________sort—convert only a quarter of the light that falls on them. Silicon has the【C2】________of being cheap: manufacturing improvements have brought its price to a point where it is snapping at the heels of fossil fuels.【C3】________many scientists would like to replace it【C4】________something fundamentally better.
John Rogers, of the University of Illinois, Urbana-Champaign, is one. The cells he has【C5】________can convert 42.5% of sunlight.【C6】________improved, Dr Rogers reckons, their efficiency could rise to 50%. Their【C7】________is that they are actually not one cell, but four, stacked one on top of another.
Solar cells are made of semiconductors, and every type of semiconductor has a【C8】________called a band gap that is different from that of other semiconductors. The band gap【C9】________the longest wavelength of light a semiconductor can absorb (it is transparent to longer wavelengths). It also fixes the【C10】________amount of energy that can be【C11】________from shorter wavelength. The result is that long-wavelength photons are lost and short-wave ones incompletely utilised.
Dr Rogers【C12】________this by using a different material for each layer of the stack. He chooses his materials【C13】________the bottom of the band gap of the top layer matches the top of the band gap of the one underneath, and so on【C14】________the stack. Each layer thus【C15】________off part of the spectrum, converts it efficiently into electrical energy and passes the rest on.
The problem is that the materials needed to make these semiconductors are【C16】________But Dr Rogers has found a way to overcome this.【C17】________solar-cell modules are completely covered by semiconductor, but in his only 0.1% of the surface is so covered. The semiconducting stacks, each half a millimeter square, are【C18】________over that surface many dots. Each stack then has a pair of cheap glass lenses【C19】________over it. These focus the sun’s light onto the stack, meaning that all【C20】________light meets a semiconductor.
【C16】
选项
A、costly
B、lively
C、orderly
D、deadly
答案
A
解析
空格所在句为表语从句,主句的主语为“问题”,故该空格所需的词应该含有否定意义。又从本文开头所述“电池材料很便宜”可推出,Rogers博士新设计的电池应为其反义词,即“昂贵的”,故A项costly为答案。B项lively“充满活力的”和C项orderly“整齐有序的”均含有肯定意义,不符合语义。根据上下文不能确定问题是否是“致命的”,故排除D项。
转载请注明原文地址:https://kaotiyun.com/show/GZY4777K
0
考研英语二
相关试题推荐
Whichofthefollowingcanbethebesttitleofthispassage?Thereasonwhythebraincellsofthepersonwhobothsmokesand
Thebesttitleforthispassagewouldbe______.Forwhatreasonarelawyerscriticized?
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Amajorreasonforconflictintheanimalworldisterritory.Themaleanimal(21)anarea.Thesizeoftheareaissufficientt
Thosedaysarelonggonewhenplacingatelephonecallmeantsimplypickingupthereceiverandaskingtheoperatortopatchyou
Notsolongago,itwasthestuffofnightmares:youpickupthelandlinetelephoneandthere’snodialingtone.Nothing.Theph
随机试题
设森林F中有三棵树,第一、第二、第三棵树的结点个数分别为M1、M2和M3。与森林F对应的二叉树根结点的右子树上的结点个数是()。
寒湿凝滞的痛经除去基本操作外还应:
患者男性,12岁。喜食煤渣,患儿缺乏的营养素是
A.月华丸B.保真汤C.补天大造丸D.麦门冬汤E.百合固金汤
砌筑水泥代号为M,强度等级不包括()。
下列各项中,属于会计数据存储介质的有()。
请你结合实际,谈谈如何作好旅游资源开发这篇大文章?
有效控制要求计划与()相适应。
(2013联考25)很多貌似过时的史学争论所代表的其实是一种力求接触人类最大多数的努力。想想有多少人已经消失在过去,他们在人数上远比如今生存在地球上的后代更多。最令人激动、最有创意的历史研究应该挖掘出事件背后那些人们所经历和体验过的人类生存状态。这类研究有
日本ではへやをしょうじでくぎっているため簡単にとりはずすことができます。へや
最新回复
(
0
)