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  3. Human vision like that of other primates has evolved in an arboreal environment. In the dense complex world of a tropical forest

Human vision like that of other primates has evolved in an arboreal environment. In the dense complex world of a tropical forest

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问题   Human vision like that of other primates has evolved in an arboreal
environment. In the dense complex world of a tropical forest, it is more
important to see well to develop an acute sense of smell. In the 【M1】______
course of evolution members of the primate line has acquired large   【M2】______
eyes while the snout has shrunk to give the eye an unimpeding view.  【M3】______
Of mammals only humans and some primates enjoy color vision. The red
flag is black to the bull. Horses live in a monochrome world. Light visible to
human eyes, therefore, occupies only a very narrow band in the whole 【M4】______
electromagnetic spectrum. Ultraviolet rays are invisible to humans though
ants and honeybees are insensitive to them. Humans have no direct perception 【M5】______
of infrared rays like the rattlesnake that has receptors tuned into  【M6】______
wavelengths longer than 0. 7 micron. The world would look eery different 【M7】______
if human eyes are sensitive to infrared radiation. Then instead of the darkness  【M8】______
of night, we would be able to move easily in a strange shadowless world
where objects glowed with varying degrees of intensity. But human eyes excel
in other way. They are in fact remarkably discerning in color gradation. 【M9】______
The color sensitivity of normal human vision is rarely surpassed even 【M10】______
sophisticated technical devices.
【M8】
选项
答案are改成were
解析 句法错误，虚拟语气。此句是典型的表示与现在事实相反的虚拟条件句，主句使用了would+ v，从句应该是用一般过去时。
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