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Two characteristics used to define mammals include

a. mammary glands and scales.
b. mammary glands and hair or fur.
c. mammary glands and sweat glands.
d. sweat glands and a four-chamber heart.

User Kiwifrog
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2 Answers

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b. they fed their child with milk from mammary gland and their body are covered up with hair or fur not feather
User Artemave
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b. mammary glands and hair or fur. things also to classify: feed milk to young, give birth live, and breathe in air, so they have lungs.
User Izaban
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