Why is the number of STRs in a specific region of the genome unique to each individual?

• A. STRs frequently undergo mutations that lead to variations that differ among individuals.
• B. STRs are inherited from parents and vary among individuals.
• C. STRs vary in presence among individuals and are not universally present.
• D. STRs are found only in non-coding regions of DNA and do not vary between individuals.

Answer: (B)