Write the Specified Quantity as a Function of the Specified $c = 2 a$

Multiple Choice

Write the specified quantity as a function of the specified variable.
-One leg of a right triangle is three times as long as the other. Write the length of the hypotenuse as a function of the length of the shorter leg.

A) $c = 2 a$
B) $c = 10 a ^ { 2 }$
C) $c = 2 \sqrt { a }$
D) $c = a \sqrt { 10 }$