This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
Myocardial isonzyme of CK which is specific for  myocardial infarction is 
Select and explain. 
A. CK-BB, B. CK-MB, C. CK-MM, D. All of the above
B: CK-MB
Answer: B: CK-MB 
Explanation: within 4–6 hrs after development of acute MI, peaks during the 2nd day (4 fold rise) and disappears in 2–3 days. Other causes of total CK elevation:
1. Skeletal diseases – Polymyositis, Muscle dys- trophy, Myopathies 
2. Electrical cardioversion
3. Skeletal muscle damage – trauma, convulsions, immobilisation 
4. Hypothyroidism 
5. Stroke 6. Surgery b. AST: Starts rising on the 1st day, peaks in 2–3 days (3 fold rise) and disappears by 3rd day. 
c. LDH1: Starts rising by second day, peaks around 3– 4 days ( 3 fold rise) and disappears in 10 days. d. Troponin T: Cardiac troponin T is a regulatory contractile protein not normally found in blood. Its detection in the circulation has been shown to be a sensitive and specific marker for myocardial cell damage. 
Troponin T and I reach a reliable diagnostic level in plasma by 12-16 hrs, maximal activity by 24-32 hrs, returns to normal in 10-12 days. Troponin I : 0-0.4 ng/ml Troponin T: 0-0.1 ng/ml Cardiac troponins are detected in the serum by using monoclonal antibodies. 
These antibodies have negligible cross reactivity to skeletal muscle. Cardiac troponins I and T start to rise within 3-4 hours after myocardial infarction and remain raised for 4-10 days