72 yo m with sob for 3 days. hx of htn and cad. receiving 2 l/min of o2 via nasal cannula. temp 37 c, p 110/min, resp 20/min, bp 150/80. bilateral crackles and wheezes. hct is 28%, leukocyte count is 8000. pulmonary artery cath shows cardiac index of 2 l/min (n = 2.5 – 4.2) and a pulmonary artery occlusion pressure of 28. abg shows ph 7.49; pco2 30; po2 58. most appropriate next step in management

I believe the answer is B)Diuretic therapy

The patient has alkalosis(pH 7.49), increased respiratory rate (20/min) and decreased carbon dioxide level(pCO2 30). These findings point to respiratory alkalosis. 
The reason for increased respiratory rate probably because of heart failure that is shown by the decreased cardiac index, pO2, crackles, and wheezes. The treatment for congestive heart failure is to decrease the preload and blood pressure by giving a strong diuretic like furosemide.