Indicate whether each of the following histone modifications adds a negative charge to the histone (A), removes a positive charge from the histone (B), or does neither of these (C). Your answer would be a four-letter string composed of letters A, B, and C only, e.g. CABA.
( ) H3 lysine 9 acetylation
( ) H3 serine 10 phosphorylation
( ) H3 lysine 4 trimethylation
( ) H3 lysine 9 trimethylation