How Do Gene Expression Arrays Differ from Comparative Genome Hybridization

How do gene expression arrays differ from comparative genome hybridization (CGH) arrays?

A) CGH arrays detect gain or loss of DNA regions; gene expression arrays detect changes in gene expression.
B) CGH arrays can interrogate hundreds of genes, while gene expression arrays test thousands.
C) CGH arrays are simpler to perform than gene expression arrays.
D) CGH arrays require co-hybridization with comparative reference nucleic acid, while gene expression arrays do not.