21.下列哪些乙狀受體阻斷劑(beta-blocker)可以用來改善低收縮分率心臟衰竭 (heart failure with reduced ejection fraction)之預後?(1)carvedilol；(2)bisoprolol；(3)metoprolol succinate；(4)xamoterol；(5)propranolol
(A)(3)+(4)+(5)
(B)(1)+(2)+(3)
(C)(1)+(2)+(5)
(D)(2)+(3)+(5)
(E)(1)+(2)+(3)+(4)+(5)