This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
What is the drug of choice to control supraventricular tachycardia- 
Select and explain. 
A. Adenosine, B. Propranolol, C. Timolol, D. Digoxin
A: Adenosine
Answer: A: Adenosine 
Explanation: Supraventricular tachycardia is a common cardiac complication of pregnancy. Treatment is the same as in the nonpregnant patient, and fetal tolerance of medications such as adenosine and calcium channel blockers is acceptable. When necessary, pharmacologic or electric cardioversion may be performed to improve cardiac performance and reduce symptoms. This is generally well tolerated by mother and fetus. ref : ( Harrison&;s principle of internal medicine,20th edition,pg no.57 )