When homologous chromosomes cross over,what occurs?

A)Two chromatids get tangled, resulting in one re-sequencing its DNA.
B)Two sister chromatids exchange identical pieces of DNA.
C)Specific proteins break the two strands and re-join them with their homologues.
D)Each of the four DNA strands of a tetrad is broken and the pieces are mixed.
E)Maternal alleles are "corrected" to be like paternal alleles and vice versa.