difficult to understand用一个英语单词替换应是什么,

to understand the problem is very difficult.(用it作为形式主语）—— ——very difficult____ underst 请问Learn to give ,underst end to cherish. Difficult to too difficult to call be difficult to do是什么意思 find it difficult to do, Difficult to lasting love rush Difficult to find the police difficult to take down everything It's difficult to choose! Really difficult to change habits? difficult to take down everything Mr.right is difficult to difficult to加什么词? prove to be difficult是什么意思? is difficult to同义词是什么 翻译Sounds difficult to everyong Difficult to unload的意思