They can ____ (容易) become unhappy when they meet problems.【这

They can ____ (容易) become unhappy when they meet problems.【这里直接是easily吗?可一般不是v+adv的么】
Bill's room is always in a real ____ (脏乱)【此处是直接dirty吗,还是说是名词】
This is a very important meeting（改为感叹句）
________ ________ important ______ this is!【这里是how还是what】
请写上为什么啊.