1.To say that language is arbitrary means something It means something to say that language is arbitrary.

对to say that language is arbitrary提问是What means something吗？ What does it mean to say that language is arbitrary? What does to say that language is arbitrary mean? 这两种对something提问的都对吗？ 

2.It is important that Tom comes. That Tom comes is important.  

对important提问是How is it that Tom comes还是How is that Tom comes?