D. Backbones.
All of the animals listed are vertebrae, a classification of animals that means they have backbones. Fish do not have legs, lungs, or hair, and birds lack hair as well.
2. Would be Hobbies.
3. Would be Hills.
4. Would be Geese.
5. Would be Churches.
6. Would be Highways.
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B - Burning down forest to clear land for planting crops
During the 1920's the economy would be recovering from the war they lost (World War 1) but in the late 1920's and early 1930's they were starting to get back up on their feet and got to full strength by 1939, which is when Hitler and his Reich started their "Blitzkrieg".