Which of the following statements is true? (T. M.) a. Continents are plates that sit on top of another plate.
b. Continents are the thinnest part of the plate.
c. Continents are the thickest part of the plate.
d. Plates and continents are located on separate plates.

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.