The most striking resemblance between birds and mammals is that both are endothermic and have four-chambered hearts. The correct option is A.
What are endothermic animals?
Endotherms are warm-blooded animals that keep a consistent body temperature in spite of their surroundings. Birds and mammals are by far the most common endotherms.
The missing options of the question are:
- They are both endothermic and have four-chambered hearts.
- They both have specialized lungs and sweat glands for cooling.
- They are both vertebrates that have specialized teeth for grinding food.
- They both undergo internal fertilization and have mammary glands to nurse their young.
The most striking resemblance between birds and mammals is that both are endothermic and have four-chambered hearts.
Thus, the correct option is A.
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