Answer:
An organ system is a group of organs that work together to perform one or more functions. Each organ has a specialized role in a plant or animal body, and is made up of distinct tissues.
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The circumference of a circle of radius
is

So, in your case, the circumference is

The circumference is actually the length of the "perimeter", so the answer to questions 1 and 2 looks the same actually
There are many possibilities. An example is
.