Which is assessed with Tanner staging?

The correct answer is D: Secondary sex characteristic. Tanner staging is a scale used to assess the development of secondary sexual characteristics during puberty. It categorizes physical changes such as breast development in females and genital growth in males. This staging system helps healthcare providers track and monitor the progression of puberty. Choices A, B, and C are incorrect as they do not directly correlate with Tanner staging. Growth hormone secretion and hormone levels may play a role in puberty but are not specifically assessed by Tanner staging. Hyperthyroidism is a medical condition unrelated to puberty development.