Final answer:
The subject of this question is Physics, specifically related to the mechanical and geometrical test of radiation therapy equipment.
Step-by-step explanation:
The subject of this question is Physics.
Physics is the branch of science that deals with the study of matter, energy, and the interactions between them. It encompasses various subfields, including mechanics, thermodynamics, electromagnetism, and optics, among others.
In the context of the question, the mechanical and geometrical test of radiation therapy equipment falls under the domain of Medical Physics. Medical Physics is a branch of Physics focused on the application of physics principles and techniques to the field of medicine, particularly in radiation therapy and imaging.