Canon EOS-1 D X Mark II Instruction Manual page 108

Lenses and Usable AF Points
Group K
AF is possible with the center AF point and the adjacent AF points
above, below, on the left, and on the right. Only the following AF area
selection modes are selectable: Single-point Spot AF, Single-point AF,
and AF point expansion (manual selection
108
).
: Cross-type AF point. Subject
tracking is superior and high-
precision focusing is achieved.
: AF points sensitive to horizontal
lines (left and right AF points
adjacent to the center AF point) or
vertical lines (top and bottom AF
points adjacent to the center AF
point). Not manually selectable. It
works only when AF point expansion
(manual selection
: Disabled AF points (not displayed).
) is selected.