Choose the correct pair.

$A:$ Myasthenia gravis is a protozoan caused disorder.
$B:$ It is affecting the neuromuscular junction leading to fatigue,weakening and paralysis of skeletal muscle.

Gout,a painful disorder of joints,is due to:

Which of the following is an incorrect statement about myasthenia gravis?
$(I)$ It is not an autoimmune disorder.
$(II)$ It affects the neuromuscular junction.
$(III)$ It occurs due to low $Ca^{++}$ in body fluid.
$(IV)$ Paralysis of skeletal muscle is a symptom of myasthenia gravis.

Old people are more liable to fracture of their bones because

Muscular dystrophy in humans is a