16. The picture shows a cube with four marked angles, $\angle W X Y$, $\angle X Y Z, \angle Y Z W$ and $\angle Z W X$. What is the sum of these angles?
A $315^{\circ}$
B $330^{\circ}$
C $345^{\circ}$
D $360^{\circ}$
E $375^{\circ}$
16. B The lengths of $W X, X Z$ and $Z W$ are all equal (each being the diagonal of a square face), hence triangle $W X Z$ is equilateral and angle $Z W X$ is $60^{\circ}$.
The other angles are all $90^{\circ}$, so the total of all four angles is $90^{\circ}+90^{\circ}+90^{\circ}+60^{\circ}=330^{\circ}$.