A nurse is teaching adolescent boys about pubertal changes. The first sign of pubertal change seen with boys is

The correct answer is D: Testicular enlargement. This is because the first sign of puberty in boys is the enlargement of the testes due to an increase in testosterone production. This occurs before other physical changes such as voice deepening, scrotal enlargement, and facial hair growth. Testicular enlargement is a fundamental and primary change that signals the onset of puberty in boys. Voice deepening and facial hair growth typically occur later in puberty, while scrotal enlargement is a secondary change after testicular enlargement. Hence, D is the correct answer as it aligns with the typical sequence of pubertal changes in boys.