Carnivorous mammals can endure what would otherwise be lethal levels of body heat because they have a heat-exchange network which kept the brain from getting too hot.
which kept
that keeps
which has kept
that has been keeping
having kept
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因为介绍了一个自然现象,所以用一般现在时,直接选择B keeps
因为介绍了一个自然现象,所以用一般现在时,直接选择B keeps
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