it's hard to navigate.中的to navigate是动词不定式吗?hard是什么成分?

it's hard to navigate.中的to navigate是动词不定式吗?hard是什么成分? it's hard to navigate.为什么要用to?如果要用的话后面动词怎么不加ing? They are willing to work hard.句中willing是表语,请问句中的动词不定式是句子什么成分 our government is working hard to save pandas中的动词不定式做什么成分 it is hard to say 中的不定式做了什么成分 it's hard to “It's hard to die. but It's hard to it's hard to tell~ it's hard to say it is hard to后跟动词不定式还是动词的ING形式 it very hard to还是it's very hard to?