11. Eight congruent semicircles are drawn inside a square of side-length 4 . Each semicircle begins at a vertex of the square and ends at a midpoint of an edge of the square. What is the area of the non-shaded part of the square?
A $2 \pi$
B $3 \pi+2$
C 8
D $6+\pi$
E $3 \pi$
11. C In the diagram the square of side-length 4 has been dissected into squares of side-length 1 . The small curved pieces have then been moved as indicated by the arrows. The resulting shaded area consists of eight squares each with area 1 , and the non-shaded area is the same.