Solution
= Solution
{c}
\b[True.] Draw two nested squares and join corresponding corners. This is the <hypercube graph>: each square gives one four-cycle and the four connecting edges give the remaining coordinate direction. The edges have no crossings, furnishing a <plane graph>.
\Image[/past-exam-of-the-probability-statistics-and-options-i-course-of-the-university-of-oxford/2007-planar-cube.png]
{title=Two nested squares give a crossing-free embedding of the <hypercube graph>}