Write the Equation for the Shape Described $y = - \sqrt { 9 - x ^ { 2 } }$

Multiple Choice

Write the equation for the shape described.
-The upper semicircle centered at (0, 0) with radius 3

A) $y = - \sqrt { 9 - x ^ { 2 } }$
B) $y = \sqrt { 3 + x ^ { 2 } }$
C) $y = \sqrt { 3 - x ^ { 2 } }$
D) $y = \sqrt { 9 - x ^ { 2 } }$