Let a Denote the Area Enclosed by the Graph $f ( x ) = \sqrt { 1 - x ^ { 2 } },$

Multiple Choice

Let A denote the area enclosed by the graph $f ( x ) = \sqrt { 1 - x ^ { 2 } },$ the x-axis, and the lines $x = 0$ and $x = 1$ . Graphing the region and using plane geometry, we can find that A is

A) $\frac { \pi } { 4 }$
B) $\frac { \pi } { 3 }$
C) $\frac { \pi } { 2 }$
D) $\pi$
E) $2 \pi$