1) Gills.
2) Small lungs.
3) Blood with a high hemoglobin concentration.
4) All of the above.
5) Answers 2 and 3, but not 1.
2) Small lungs.
3) Blood with a high hemoglobin concentration.
4) All of the above.
5) Answers 2 and 3, but not 1.
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Probably your teacher wants this one.
3) Blood with a high hemoglobin concentration.
I'm rejecting the "small lungs" choice. Dolphins don't have smaller lungs than terrestrial mammals. Eyeballing other marine tetrapods, most of them don't look like they have smaller lungs. It's hard to tell with the snakes though.
3) Blood with a high hemoglobin concentration.
I'm rejecting the "small lungs" choice. Dolphins don't have smaller lungs than terrestrial mammals. Eyeballing other marine tetrapods, most of them don't look like they have smaller lungs. It's hard to tell with the snakes though.