Answer:
Each of her parents must have one recessive gene for blond hair color
Step-by-step explanation:
- Blond is a recessive trait
- Since Silvia is blond this means she has both copies of the recessive gene for hair color
- Therefore, both her parents have a recessive gene for blond hair and passed it down to her.
- The parents don't have blond hair because their dominant gene for browns masks the recessive gene for blond.