Find the Length of the Third Side of the Right $c$

Multiple Choice

Find the length of the third side of the right triangle. Assume that $c$ represents the length of the hypotenuse. Give an exact answer and, if appropriate, an approximation to three decimal places.
- $a=\sqrt{6}, c=2 \sqrt{3}$

A) $b=\sqrt{6}, b \approx 2.449$
B) $b=6$
C) b $=2 \sqrt{6}, b \approx 4.899$
D) $b=\sqrt{7}, b \approx 2.646$