A scientist wants to find the percent of teens that like the taste of "brand X" lemonade over "brand Y" lemonade. She conducts a taste test of 500 teenagers. She gives each teen a bottle of lemonade with the labels showing the brand of each lemonade. She asks each teenager to taste each brand after drinking water in between. She finds that 50% of teens like brand X and 50% like brand Y lemonade. Why are the results of the survey most likely unreliable?

Adults were not interviewed.
Not enough teens were interviewed.
The investigation was based on taste.
The lemonade labels introduced bias.