以下关于各类民事法律行为之间关系的表述中正确的是( )。

A．双方民事法律行为都是双务民事法律行为

B．单务民事法律行为都是单方民事法律行为

C．有偿民事法律行为都是双务民事法律行为

D．实践性民事法律行为都是要式民事法律行为

They planned to go to Guangzhou to watch the Asian Games, but because of their daughter's unexpected

illness they had to stay at home ____. [ ]

A. otherwise

B. anyhow

C. however

D. instead