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

Which of the following does not follow the law of independent assortment?

When a test cross is performed between $F_1$ hybrid flies,the parental type offspring are produced in much higher frequency than the recombinant type offspring. What does this indicate?

The map distance between genes $A$ and $B$ is $3$ units,between $B$ and $C$ $10$ units,and between $C$ and $A$ $7$ units. The order of the genes in a linkage map constructed on the above data would be:

Which of the following statements are correct?

Continuous variations are attributed to