We didn't enjoy the day ______ the weather was so awful.[ ]

A. until  

B. because  

C. unless      

D. even though

已知H2S的Ka₁=9.1×10^-8，Ka₂=1.1×10^-12，则0.100mol/dm³H₂S溶液的pH值为( )。

A．4.23
B．4.53
C．4.03
D．5