20. Transcription of gene X is controlled by transcription factor A. Gene X is only transcribed when factor A is phosphorylated. Data on the tissue distribution of factor A and the activities of a protein kinase and a protein phosphatase specific for factor A are presented in the table below.Of these three tissues, gene X will be transcribed in (A) muscle only (B) heart only (C) brain only (D) brain and heart only (E) muscle, heart, and brain