Answer: A. Metaphysics/epistemology
Explanation: The systematic inquiry or investigation into the standards and presuppositions of any field of study is refered to as philosophy. The two major branches of philosophy are Metaphysics and epistemology. Metaphysics is simply refered to as the study of what is beyond the physical e.g; soul, ghost, Angels etc. While Epistemology simply means study of how we know what we know i.e the origin of knowledge.