D is incorrect because if Zuhur visits Ghana in the second month, that forces our YW block into months 3 and 4, respectively. That leaves 1 V needed to still be placed in G (as indicated by rule 1) and the only month left in G is month 1. With V in month 1 in G, that does not allow V to visit G at some time between the visits to I.
C can be diagrammed as:
F: Z Z Y Z
G: Y V Y W
I: V W V W
Nicholas-Groblewskion August 15, 2020
I think you made a mistake in your explanation; no representative can visit two sites in the same month.
Seoon August 21, 2020
The explanation seems to have some errors as Nicholas points out.
The diagram for C should be:
F: Z Y Z Z
G: Y V Y W
I: V W W V
