You are hiking the Inca Trail on the way to Machu Picchu. When you arrive at the highest point on the trail, which of the following are possibilities? In alphabetical order without punctuation or spacing, list the letters which indicate possibilities.

(A) The path passes through the center of a set of concentric contour lines.
(B) The path is tangent to a contour line.
(C) The path follows a contour line.
(D) The path crosses a contour line.

Possibilities: