Covalent modifications of enzymes include (  )A:Phosphorylation and dephosphorylation B:acetylation and deacetylation C:Methylation and demethylation D:adenosylation and deadenylation 答案: Phosphorylation and dephosphorylation;acetylation and deacetylation;Methylation and demethylation;adenosylation and deadenylation