When closely placed genes on the same chromosome are inherited together,the phenomenon is known as:

Genes $A$ and $B$ are linked. What will be the genotypes of the offspring produced from a cross between $AB/ab$ and $ab/ab$?

Which of the following is true about linkage?
$I.$ It is a phenomenon in which more recombinants are produced in $F_{2}$-generation.
$II.$ More parental combinations are produced in $F_{2}$-generation.
$III.$ Genotypes which are present in $F_{1}$ hybrid reappear in high frequency in $F_{2}$-generation.
$IV.$ It is a phenomenon in which two chromosomes are linked.

Mendel observed that some characters did not assort independently. Later researchers found it to be due to

Total number of linkage groups in honeybee is . . . . . . .

There are three genes $a, b,$ and $c$. The recombination frequency between $a$ and $b$ is $20\%$,between $b$ and $c$ is $28\%$,and between $a$ and $c$ is $8\%$. What is the possible arrangement of these genes on the chromosome?