问题：
[单选题]Two liquid phases are in equilibrium at 2 bar. The bottom liquid is pure A; the top liquid is a mixture ofA and B with xA=0.05. If PAsat=0.5 bar, Pesat=0.8 bar, the fugacity of liquid A in the mixture is bar.
A.1.0
B.0.8
C.0.5
D.0.1
E.0.05
