Incomplete linkage is $A$. Complete linkage is $B$. Choose the correct option for $A$ and $B$.

The linkage map of a fruit fly has a total map distance of $66$ units. The gene for yellow body $(a)$ is at one end and the gene for short hair $(y)$ is at the other end. What will be the recombination frequency between these two genes $(a$ and $y)$?

The first attempt to demonstrate linkage in plants was made in $.....$.

Which of the following combinations of characters selected by Mendel shows linkage?

There are three genes $a, b, c$. The percentage of crossing over between $a$ and $b$ is $20\%$,between $b$ and $c$ is $28\%$,and between $a$ and $c$ is $8\%$. What is the sequence of genes on the chromosome?

The term "linkage" was coined by