The correct answer is a - a form of a gene. An allele refers to one of the alternative versions or variations of a gene that can exist at a specific location on a chromosome. In other words, alleles are different versions of the same gene. They can differ in their DNA sequence, which ultimately results in different traits or characteristics. To determine the answer to this question, you can rely on your prior knowledge of genetics or consult reliable sources such as textbooks or reputable websites.
