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Which of the following is not am example of a polymer? protein nylon kevlar concreta

In a stagnant pool of water, a crayfish may spend much of its time lying with one side of its carapace near the surface of the water. in this position, it will move the walking legs on that side in a rhythmic back-and-forth motion. explain the likely function of this behavior.

Alfred pushes on a heavy box, but cannot move it. the box has a lot of inertia motion friction gravity