The area of a circle is equal to the radius squared times pie, basically:

The radius is 3, so we multiply 3 times 3 times pie to get the area.
You're gonna want to plug in the following into a calculator:

After getting 28.26 from such calculator, you need to round to the tenths place. In this number, the tenths place is the 2 next to the decimal on the right. Because the number after the 2 is a 6, that means we need to simplify the answer to (28.3). When you are rounding a number, you look at the number to the right, if it is 5 or bigger, add one and remove the rest, if it is less than 5, just get rid of the rest and leave it as it is.
Answer:
Option (C)
Step-by-step explanation:
In the given circle, AB is a chord passing through the center O.
Therefore,chord AB is a diameter of the circle and OC is the radius.
AO = OB = OC
OC⊥AB, and length of OC = 7 cm
By applying Pythagoras theorem in right ΔBOC,
BC² = OC² + OB²
BC = 
= 
=
≈ 9.9 units
Therefore, Option (C) will be the answer.