Which of the following is an exception to Mendel's laws?

Which scientist explained linkage and recombination in Drosophila?

Morgan hybridized yellow-bodied,white-eyed females to brown-bodied,red-eyed males and intercrossed their $F_{1}$ progeny. He observed that:
$(a)$ $F_{2}$ ratio deviated significantly from the $9 : 3 : 3 : 1$ ratio.
$(b)$ Both genes did not segregate independently of each other.
$(c)$ Recombinant types are not obtained in $F_{2}$ generation.
$(d)$ Both genes segregate independently of each other.
Select the correct set of statements:

Which method can be used to determine the location of specific genes on a chromosome?

Linked genes are separated by:

In maize,the chromosome number is $2n = 20$. The number of linkage groups in it shall be: