Although the number of genes in the human genome is surprisingly low compared to less complex organisms, the number of possible products from those genes is greatly amplified by __________.

• A. each gene being activated by a unique combination of control elements and activator molecules
• B. coordinate control of genes on different chromosomes
• C. the congregation in specific sites in the nucleus of genes involved in related metabolic processes but on different chromosomes
• D. differential activation of genes in different cell types
• E. alternate arrangements of exons from a primary transcript