Group Mean Centring Is a Useful Way to Prevent Multicollinearity

Group mean centring is a useful way to prevent multicollinearity, but how is it usually calculated?

A) An individual score (player confidence) is subtracted from a group mean (mean player confidence in that group) .
B) An individual score (player confidence) is multiplied by the group mean (mean player confidence in that group) .
C) An individual score (player confidence) is added to a group mean (mean player confidence in that group) .
D) An individual score (player confidence) is divided by a group mean (mean player confidence in that group) .