Please help! i don’t get any of this.

If the line in the circle goes halfway through it is the radius but, if it goes all the way it is the diameter.

Step-by-step explanation:

B.

1. The line goes through halfway = radius(r)

2. Take (r)= 3mm and use the formula C= 2 x Pie x r (3)

Type into calculator

It is the same for b, d, and e

C.

1. the line goes all the way through = diameter (d)

2. Take (d)= 15mm and use in the diameter formula C= Pie x d (15mm)

Note you do not times the diameter x2 because it goes ALL the way through the circle.

Unlike the radius that goes halfway through so you need to x2 or double it to get the full circumference

Hope This Helps ( also make sure to put the units in your answer mm,cc,etc)

a is the right answer