Which of the following characteristics best explains why whales are classified as mammals rather than fish?以下哪一項特徵最能解釋為什麼鯨魚被歸類為哺乳類而非魚類？
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They breathe air using lungs and give live birth to nurse their young with milk. 他們用肺呼吸空氣，產下活的幼崽並用乳汁哺育 Like all mammals, whales are warm-blooded (or maintain high metabolic body heat), breathe air through lungs, give birth to live young, and nurse them with mammary glands. 與所有哺乳動物一樣，鯨魚是溫血動物（或維持高度代謝體熱）、用肺呼吸空氣、胎生並以乳腺哺育幼崽。 Whales are warm-blooded and have smooth skin with little to no hair, rather than scales. 鯨魚是溫血動物，且擁有光滑且幾乎沒有毛髮的皮膚，而不是鱗片 Whales do not lay eggs; they give birth to live young. 鯨魚不會產卵；它們是直接產下活生生的幼崽。