47. The uppermost figure above shows the locations of four genes on the genetic map of an organism; the lower figure shows the locations of the same four genes on a physical map derived from the nucleotide sequence of the DNA of that organism. The maps are not identical because (A) there is no relationship between the position of genes in a genetic map and their positions on the DNA (B) recombination frequencies per kb of DNA are not uniform throughout a chromosome (C) the farther apart two genes are, the more likely they are to recombine (D) the closer two genes are, the more likely they are to recombine (E) some genes contain introns