What are the two main reasons for including covariates in ANOVA?

A. (1) To reduce within-group error variance (2) Elimination of confounds
B. (1) To increase within-group error variance (2) To reduce between-group error variance
C. (1) To increase within-group error variance (2) To reduce between-group error variance
D. (1) To increase between-group variance (2) To reduce within-group error variance