5. (10th "Hope Cup" Invitational Competition Question) A cube with an edge length of 1 and its circumscribed sphere intersect with a plane to form a circle and its inscribed equilateral triangle. The distance from the center of the sphere to this section is ( ).
A. $\sqrt{3}$
B. $\frac{\sqrt{3}}{3}$
C. $\frac{\sqrt{3}}{6}$
D. $\frac{\sqrt{3}}{12}$
5. C. Reason: From the given conditions, we know that the three vertices of the inscribed equilateral triangle in the cross-sectional circle are the other endpoints of the three edges sharing a common vertex in the cube. It is easy to calculate that the distance from the center of the sphere to the cross-section is $\frac{1}{6}$ of the length of the cube's space diagonal.