The elbow joint is extremely stable because

The bony surfaces of the humerus and ulna interlock, the articular capsule is very thick, the capsule is reinforced by stout ligaments

i am positive it is c. condensing but i may be wrong

metamorphism is the change of minerals or geologic texture (distinct arrangement of minerals) in pre-existing rocks (protoliths), without the protolith melting into liquid magma (a solid-state change). the change occurs primarily due to heat, pressure, and the introduction of chemically active fluids. i hoped i !