Crossing over between homologous chromosome never exceeds

Answer: Option A

Crossing over between homologous chromosomes never exceeds 50%.
The recombination frequency between two genes cannot be greater than 50% because a random assortment of genes generates 50% recombination.
Non-linked genes produce 1 : 1 parental to non-parental. Thus, the recombination frequency would be non-parental/total, i.e. $$\frac{1}{1+1}=50\%.$$