In meiosis, recombination occurs:
(A) during prophase I and II and involves exchange of chromosome fragments between sister chromatids.
(B) only during prophase I and involves exchange between chromatids of homologous chromosomes.
(C) only during prophase I and involves exchange of chromosome fragments between sister chromatids.
(D) during prophase I and II and involves exchange of chromosome fragments between all four chromatids.