I'll give brainlist
Which of the following most likely accounts for regional differences in the
types of crops grown, the types of homes built, and the types of clothing
worn in mid-nineteenth century China? *
A. Nationalist sentiments
B. Geography and climate
C. Social and economic mobility
D. Imperialist government policies

I'm pretty sure there's a geometry rule for   anyways, if the triangle is equilateral, and the circle is circumscribed, the circle is outside of the triangle.  to find the area, you need the radius.  the radius should be a straight line from the center of the triangle to any of it's points.  draw lines from the center of the circle to each of the triangle points.  draw three more lines from the center to the middle of the sides of the triangle.  you should now have six separate 30-60-90 triangles inside of your original triangle. use your 30-60-90 rules to solve for the radius, then the circumference. 

The answer for your problem would be a. 7

Do you have a picture for this problem?