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
Which of the following has been shown to prolong life in patients with chronic congestive heart failure but has a negative inotropic effect on cardiac contractility? 
Select and explain. 
A. Carvedilol, B. Digoxin, C. Enalapril, D. Furosemide
A: Carvedilol
Answer: A: Carvedilol 
Explanation: None