In which two cases (listed below) is it be impossible to
identify recombination between two genes W and Z
(with alleles W, w, Z, z) if
you cross a heterozygote WwZz with a recessive homozygote
wwzz and analyze the offspring for the phenotypes. The
alleles W and Z are linked on one chromosome and
w and z are linked on the other chromosome in the
heterozygous parent and the heterozygous parent is capable of
recombination during meiosis:

1: if a single cross-over occurs between the two genes

2: if a double cross-over occurs between the two genes

3: if a single cross-over occurs outside of the region between W
and Z

4: if a triple cross-over occurs between W and Z

A) both 1 and 2

B) both 1 and 3

C) both 2 and 3

D) both 2 and 4

E) both 1 and 4

“The answer is C. Please tell me how to approach the problem and
get the answer”