题目

下列事实与氢键有关的是 ( ) A．水加热到很高的温度都难以分解 B．HF、HCl、HBr、HI的热稳定性依次减弱 C．氨易液化，氨极易溶于水       D．CH4、SiH4、GeH4、SnH4的熔点随相对分子质量增大而升高 答案：C Have you got any explanation to the question ________ he came here for the day before yesterday? [　　] A．why B．what C．how D．which