A

Compliance = ΔV / ΔP.  The tidal volume inspired is 500 mL = 0.5 L, and intrapleural (hence transpulmonary) pressure became 5 cm H₂O more negative (-4 → -9 cm H₂O), so  
C = 0.5 L ÷ 5 cm H₂O = 0.1 L /cm H₂O, matching option A.  This method (volume change divided by transpulmonary pressure change) is the standard way pulmonary compliance is calculated [Hylkema, 1983, PMID 6831897].