Compare their blood types. Compare their handwriting. Compare their genes. Compare their fingerprints.
I gave my students this multiple choice question: Which of the following is the best way to determine whether two people are related?

Only one answer is correct among these 4 choices:
- Compare their blood types.
- Compare their handwriting.
- Compare their genes.
- Compare their fingerprints.

Could you tell me which one is correct?

Compare their genes.