Answer: girls tend to outweigh boys in adolescence
Explanation:
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the answer is Air and Water pollution.
Answer:
Birds’ feathers are designed to be light but very strong, flexible but very tough. Although it looks like feathers grow all over a bird, they actually grow in specific areas called feather tracks. In between the feather tracks are down feathers. This keeps the body weight down.
Feathers are made of a tough and flexible material called keratin. The spine down the middle, called the shaft, is hollow. The vanes are on the two halves of the feather. They are made of thousands of branches called barbs. Because there are many spaces between these barbs, a feather has as much air as matter.
Explanation:
