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
True about esmolol is: a) It is a cardioselective β–blocker b) It increases airway resistance c) It causes tachycardia d) Its t 1/2 is 4 hrs e) It has negative inotropic activity 
Select and explain. 
A. de, B. cd, C. ae, D. bc
C: ae
Answer: C: ae 
Explanation: Esmolol is an ultrashort acting β-blocker (t1/2 < 10 min.)
It is inactivated by esterases in blood.
β-blocker decreases heart rate and force of contraction (negative inotropic action).
Beta blockers can precipitate or aggravate CHF.
Selective beta 1 blocker and are less likely to cause bronchoconstriction, thus do not increase airway resistance.