The circumfrence of a circle is equal to pi times its diameter.
In this question, the diameter is 63 inches, and we are using 22/7 for pi.
This puts the circumfrence at 63 ×22/7 = 198 inches.
There are 360° in a circle, so an 120° sector will be 1/3 of the circle.
1/3 of the circle will have 1/3 of its circumfrence.
198 ÷ 3 = 66, so the arc we're planting marigolds on is 66 inches long.
If each marigold is ~8 inches apart, how many would we need?
Well, 66 ÷ 8 = 8¼, but we can't have a fraction of a marigold, so we round up to 9.
The answer is C) 9 marigolds.