Which of the following represents the frequency of recombination between two genes that are inversely proportional to the strength of linkage?

In a fruit fly,the $X$-chromosome linkage map has a total length of $66$ units,with the yellow body gene $(y)$ at one end and the bobbed hair gene $(b)$ at the other end. What will be the recombination frequency between these two genes $(y$ and $b)$?

The recombination frequency between genes $B$ and $A$ is $5\%$. The recombination frequency between genes $A$ and $C$ is $15\%$. What is the possible sequence of these genes on the chromosome?

Linkage with increasing age becomes ......

Two genes '$a$' and '$b$' show $20\%$ recombination. What will be the proportion of gametes produced by a dihybrid $F_1$ individual with the genotype $++/ab$,derived from a cross between $++/++$ and $ab/ab$?

The phenomenon that acts against linkage is......