They work well together－her steadiness(稳健) acts as a(n)      to his clever but often impractical ideas.

A．award

B．belief

C．balance

D．contrary

炎热的夏夜里，柳倩在一间密封性能好的房间里开空调睡觉，隔天早晨起床，柳倩发现铝合金门窗的玻璃变得模糊不清了，这是什么原因？仔细想想，水珠附着在玻璃的内表面还是外表面？