When cpg islands are unmethylated,
a) chromatin in the promoter region is open, allowing access by transcription factors and rna polymerase
b) chromatin in the promoter region is closed, preventing transcription factors and rna polymerase from binding
c) chromatin in the enhancer region is closed, so they are unable to bind regulatory proteins to initiate transcription
d) dnase hypersensitivity in that region of the chromosome is lost
e) genes downstream of the cpg islands cannot be expressed, because the promoter region is blocked by histones