At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes. There was surprise expressed by many that the number of protein-coding sequences was much smaller than they had expected. Which of the following could account for most of the rest?

A) “junk” DNA that serves no possible purpose B) rRNA and tRNA coding sequences C) DNA that is translated directly without being transcribed D) non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function E) non-protein-coding DNA that is transcribed into several kinds of small RNAs without biological function