Select all the reasons why strs are commonly examined in dna profiling.

STRs is an abbreviation for "Short Tandem Repeats," which are repeated DNA segments, around 2-6 base pairs long. 
 
It is also used in DNA typing/profiling to compare specific loci on DNA from two or more samples. It is commonly used in forensic analysis to distinguish one DNA profile to another because there is very little chance that the STR pattern at all the loci of the DNA of one person is identical to another (unrelated person). In addition, the high variability in the number of repeats of the STRs makes it extremely variable to discriminate DNAs of different individuals. 

The answer is c : ) hope this answered your question!