The nematode Caenorhabditis elegans A) is composed of a single cell, in which the developmental origin of each protein has been mapped. B) is composed of about 1,000 cells, in which the developmental origin of each cell has been mapped. C) has only a single chromosome, which has been fully sequenced. D) has about 1,000 genes, each of which has been fully sequenced. E) uniquely, among animals, utilizes programmed cell death during normal development.