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: Pharmacology
Calcium channel blockers are not useful in: 
Select and explain. 
A. Arrhythmia., B. Angina., C. Hypertension., D. Sick sinus syndrome.
D: Sick sinus syndrome.
Answer: D: Sick sinus syndrome. 
Explanation: Calcium channel blockers and beta-blockers are contraindicated in sick sinus syndrome.