重慶醫科大學2013年考博英語完形填空試題

The human nose is an underrated tool. Humans are often thought to be insensitive smellier compared with animals, 1 this is largely because, 2 animals, we stand upright. This means that our noses are 3 to perceiving those smells which float through the air, 4 the majority of smells which stick to surfaces. In fact 5 , we are extremely sensitive to smells, 6 we do not generally realize it. Our noses are capable of 7 human smells even when these are 8 to far below one part in one million.