Which of the following diseases is a genetic disorder and causes progressive degeneracy of the skeletal muscle?

The correct option is B Muscular dystrophy
Muscular dystrophy - It is a genetic disorder which is caused by the progressive degeneration of skeletal muscles. Muscles are damaged and causes difficulty in walking, swallowing and even breathing.
Osteoporosis- it is an age-related disease which is caused by the decreased level of estrogen in our body or increased levels of cortisone among various other causes. This also increases the chances of fractures. In this bone density is reduced to a large extent and the chances of bones to break increase a lot.

Myasthenia gravis is an autoimmune disease in which our immune system mistakenly attacks our healthy body cells. It is a neuromuscular disease which causes skeletal muscle weakness. Eyes and faces are most commonly affected by this. It results in double vision, drooping eyelids, trouble while talking and walking, etc.