Assertion : Myasnia gravis is an autoimmune disease.

Reason : Immune system rejects  transplant muscles.

Amphetamine is one of the drugs included in the 'dope test' for athletes. Amphetamines are found in the urine soon after ingestion. Since metabolism of amphetamines is slow, the drug is found in the urine for several subsequent days. If the drug is found in the urine test of athletes, they are debarred to participate. Amphetamines are synthetic activator of sympathetic nerves bringing about increased activity and alertness. They are used by some persons to work continuously for hours or to reduce weight. They reduce mental capability. The drugs are addictive.

So, the correct answer is 'Assertion is correct but Reason is incorrect'.