A circle has a radius of $4 \mathrm{~cm}$. A line segment joins two points on the circle. What is the greatest possible length of the line segment?
(A) $10 \mathrm{~cm}$
(B) $8 \mathrm{~cm}$
(C) $4 \mathrm{~cm}$
(D) $12 \mathrm{~cm}$
(E) $6 \mathrm{~cm}$
The line segment with greatest length that joins two points on a circle is a diameter of the circle. Since the circle has a radius of $4 \mathrm{~cm}$, then its diameter has length $2 \times 4 \mathrm{~cm}=8 \mathrm{~cm}$, and so the greatest possible length of the line segment is $8 \mathrm{~cm}$.

ANSWER: (B)