Final answer:
Leptin and peptide YY (PYY) both contribute to a sense of fullness, with leptin having a longer-term effect and PYY an immediate effect on reducing appetite. The correct option is d.
Step-by-step explanation:
The hormones that contribute to a sense of fullness are leptin and peptide YY (PYY). Leptin is a protein hormone secreted by adipose tissues in response to food consumption that promotes satiety, which is a feeling of fullness that signals us to stop eating.
Unlike leptin, which acts over the longer-term to regulate energy balance, PYY is released by the gut in response to food and has a more immediate effect on reducing appetite. Therefore, the correct answer to the question is d. A and B only.