Linkage Between Genes Causes Them to Be Inherited Together and Reduces

Linkage between genes causes them to be inherited together and reduces recombination; crossing over breaks up the associations of such genes. In a testcross for two linked genes, each crossover produces two recombinant gametes and two nonrecombinants. The frequency of recombinant gametes is half the frequency of crossing over, and the maximum frequency of recombinant gametes is 50%.
-For single crossovers, the frequency of recombinant gametes is half the frequency of crossing over because

A) a test cross between a homozygote and heterozygote produces 1/2 heterozygous and 1/2 homozygous progeny.
B) the frequency of recombination is always 50%.
C) each crossover takes place between only two of the four chromatids of a homologous pair.
D) crossovers occur in about 50% of meioses