Lack of independent assortment between two genes A and B in fruitfly Drosophila is due to
The tendency of presence of genes in very close with one another is called Linkage. The genes, exhibit linkage is said to be Linkage group, and the genes are called Linked genes. Linked genes cannot separate and are inherit together. In Drosophila, the two genes A and B are present on the same chromosomes are expressing linkage. In these conditions, Law of independent assortment, explained by Mendel is not possible.
So, the correct option is ‘Linkage’.