At first, the speaker was referring to the problem of pollution in the country, but halfway in her speech, she suddenly ___ to another subject.
He refused to ___ that he was defeated.
An individual human existence should be like a river—small at first, narrowly contained within its banks, and rushing passionately past rocks and over waterfalls. Gradually the river grows wider, the banks recede, the waters flow more quietly, and in the end, without any visible break, they become merged in the sea, and painlessly lose their individual being. The man, who, in old age, can see his life in this way, will not suffer from the fear of death, since the things he cares for will continue. And if, with the decay of vitality, weariness increases, the thought of rest will not be unwelcome. I should wish to die while still at work, knowing that others will carry on what I can no longer do and content in the thought that what was possible has been done.
The human nose is an underrated tool. Humans are often thought to be insensitive smelters compared with animals, 21 this is largely because, 22 animals, we stand upright. This means that our noses are 23 to perceiving those smells which float through the air, 24__ the majority of smells which stick to surfaces. In fact, __25__, we are extremely sensitive to smells, __26 we do not generally realize it. Our noses are capable of 27 human smells even when these are 28 to far below one part in one million.Strangely, some people find that they can smell one type of flower but not another, __ 29__ others are sensitive to the smells of both flowers. This may be because some people do not have the genes necessary to generate 30 smell receptors in the nose, These receptors are the cells which sense smells and send 31 to the brain, However, it has been found that even people insensitive to a certain smell 32 can suddenly become sensitive to it when 33 to it often enough.The explanation for insensitivity to smell seems to be that brain finds it 34 to keep all smell receptors working all the time but can 35 new receptors if necessary. This may __36__ explain why we are not usually sensitive to our own smells—we simply do not need to be. We are not 37 of the usual smell of our own house but we 38 new smells when we visit someone else’s. The brain finds it best to keep smell receptors 39 for unfamiliar and emergency signals __40__ the smell of smoke, which might indicate the danger of fire.
我国高等教育大众化过程需要更加关注4个问题：理解高等教育规模扩大的本原，加强人文素质教育，平衡优秀与平等的关系，协调大学与政府、市场间的关系。所有这些都要以明析高等教育哲学的一个根本问题为前提，即大学的根本使命和目标如何定位的问题。现代大学一定要使学生和公众都能够理解大学最终和最基本的使命是什么。大学不是提供获利的手段和就业单位的场所，而是要激发他们理性的光辉和力量，培养学生坚持长远地、全面地看待个人、社会与历史的发展所需要的能力。
Amplifiers such as those in computers and sound reproducing systems are responsible for ______ an erratic input signal.