Canon EOS-1D X Mark II DSLR Camera (Body Only) - Manual (Page 483)

483
B Button Functions
When you press the < W >, < o >, < Q >, < S >, < i >,
< O >, or < B > button, the setting screen will appear and you can use
< 6 >, < 5 >, < 9 >, and < B > to set the function.
Button Operation for the Quick Control and
Custom Quick Control Screens
Shooting mode AF operation / Drive mode
AF point selection Metering mode/
Flash exposure compensation
ISO speed Exposure compensation
White balance AEB