What Is the Distance,in Atomic Radii,along Any Edge of a Face-Centered

Multiple Choice

What is the distance,in atomic radii,along any edge of a face-centered unit cell?

A) $\frac{4 \times r}{\sqrt{3}}$
B) 2 × r
C) 4 × r
D) $2 \sqrt{2} \times r$
E) r