A) Alzheimer's - (2) -it is a neuronal disorder related to the brain -
Alzheimer's disease is an irreversible, progressive brain disease that slowly destroys memory and disorders cognitive function( remember, problem-solve, and pay attention etc)
(B) Tetanus - (3) - It is caused by low calcium levels(Hypocalcemia) in muscles -Hypocalcemia is the primary cause of tetany. Low ionized calcium levels in the extracellular fluid increase the permeability of neuronal membranes to sodium ion, causing a progressive depolarization, which increases the possibility of action potentials.
(C) Myasthenia gravis - (1) -It is an autoimmune disorder which may lead to paralysis in muscles -It is mainly due to the decrease in the number of acetylcholine receptors at neuromuscular junctions due to an antibody-mediated immune attack(autoimmune disorder).
(D) Gout - (4)-It is related to the accumulation of uric acid crystals -Gout is a type of arthritis, the disease caused by the disorder of uric acid metabolism in which uric acid crystals are accumulated in joints, tendons and surrounding tissues which leads to inflammation and pain.
So, the correct option is 'A-2, B-3, C-1, D-4'.