Indicate whether each of the following histone modifications is generally associated with active genes (A) or silenced genes (S). Your answer would be a four-letter string composed of letters A and S only, e.g. SSAS.
( ) H3 lysine 9 acetylation
( ) H3 serine 10 phosphorylation
( ) H3 lysine 4 trimethylation
( ) H3 lysine 9 trimethylation