Final answer:
The correct answer is C) Anatomy and physiology, which is a crucial aspect of a medical assistant's knowledge base.
Step-by-step explanation:
The knowledge base of the modern medical assistant includes Anatomy and physiology. This field is fundamental to any career in the health professions and provides essential information on the function and structure of the human body. Knowledge in anatomy and physiology is key to making healthful choices and understanding various medical conditions, treatments, and procedures. It is incorrect to classify astrology as a natural science; it is considered a pseudoscience and does not adhere to scientific methods. Botany, while a branch of biology, is more specific to plants and not directly related to the daily responsibilities of a medical assistant. Quantum physics, although a fundamental branch of physics, does not directly apply to medical assistant duties.