Since you haven't provided the radius, I'll just use the symbol 'r' to refer to radius. You can substitute with the given radius in the equation.
Now, circumference of the circle is calculated using the following rule: curcimference of circle = 2*pi*r where: r is the radius pi is given as 3.14 Therefore: circumference of circle = 2*3.14*r = 6.28 r units
Quadratic equations always have a degree of 2. That means that we will always have an x² term. Of the 4 choices, only A and B offer a term of x², making them a quadratic.
