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

• A
  $A$ and $B$ both are correct
• B
  $A$ and $B$ both are incorrect
• C
  $A$ is correct and $B$ is incorrect
• D
  $A$ is incorrect and $B$ is correct