Which of the following pairs of chemical substances is correctly categorized?

Pepsin is a digestive enzyme secreted in the stomach, while prolactin, also known as luteotropin, is a protein hormone known for its role in enabling females to produce milk. Secretin is a polypeptide hormone that regulates water homeostasis, while rhodopsin belongs to the G-protein-coupled receptor family. Troponin and myosin are complex regulatory proteins in skeletal muscle fibers. So, the correct answer is option B.