What Is the Length of the Diagonal (In Atomic Radii) $\frac { 4 \times r } { \sqrt { 3 } }$

Multiple Choice

What is the length of the diagonal (in atomic radii) along the face of a face-centered cubic unit cell?

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