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.
- $\mathrm{a}=9, \mathrm{~b}=9$

A) $\mathrm{c}=\sqrt{162} ; \mathrm{c} \approx 12.728$
B) $\mathrm{c}=\sqrt{82} ; \mathrm{c} \approx 9.055$
C) $\mathrm{c}=\sqrt{18} ; \mathrm{c} \approx 4.243$
D) $\mathrm{c}=9$