连科学家不知道大脑，思想何始何终。
Scientists don't know where the brain ends and the mind begins.
但科学家不知道它们为什么发出这样的声音，因此研究人员对这种发音行为进行了研究。
But they hadn't known what these sounds were for. So researchers examined how the vocalizations might correspond with behavior.
科学家们不知道有多少噪音以及何种噪音对海洋动物有害。
Scientists do not know how much and what kinds of noises are harmful to ocean animals.
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