How many linkage groups are present in bacteria?

Which of the following statements is not true of two genes that show $50\%$ recombination frequency?

For the preparation of genetic maps,the recombination frequencies between genes are additive over short distances but not over long distances due to

Continuous variations are attributed to

Genetic variation is observed in sexually reproducing species.

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?