Answer:
The correct answer is c. proteins.
Step-by-step explanation:
Internal and external regulators in biological processes are often associated with proteins. These regulators can control various cellular functions, including cell division and growth. Proteins like cyclins and cyclin-dependent kinases (CDKs) are examples of internal regulators that help regulate the cell cycle. External regulators can include growth factors and hormones, many of which are also proteins, that influence cell behavior and function. Lipids and carbohydrates are essential biomolecules in their own right but are not typically associated with the role of cellular regulation.