is to do sthis后面不是应该加ing形式吗?什么时候是to do的?

is to do sthis后面不是应该加ing形式吗?什么时候是to do的? all I have to do is后面用动词原型还是to do?我觉得is后面应该跟to do,但很多时候不是这样的,比如以下几句都是is 后直接跟动词原型,好象不合语法嘛：All I have to do is do what I wanna do!All i have to do is It is dangerous swimming in the sea in stormy weather.be dangerous 后面不是应该接to do 这里dangerous后面为什么不用to do,而用doing 形式 rather than不是介词词组吗?为什么prefer to do rather than do中rather than后面加do?介词后面不是应该加doing吗? rather than不是介词词组吗?为什么prefer to do rather than do中rather than后面加do?介词后面不是应该加doing吗? belong+sThis telephone belongs to that boy.belong是否+s,取决于前面的telephone,还是后面的boy? 那prepare 后面不是to do 不是doing啊 there's nothing for them to do but ____ silence.请问这空是填to remain 还是remain,各个感觉应该是填remain,因为前面有实义动词的do,后面不是应该省略to吗,但是答案是to remain.There is nothing left to him but to hit ba none is afraid of difficulties,do they?请问后面的反义疑问为什么用do,主句用的是is,后面不是应该和主句一样用is的么? This is Nancy.She is _____the USA. She likes sThis is Nancy.She is _____the USA. She likes swim . _____应该填( ? ) 什么是宾语?All (that)you have to do is to press the button.中的that为什么是宾语?不是应该跟在动词后面吗?The first step that we are to take is very different.中的THAT为什么是宾语?I can lend you any books that you want. He doesn't seem to be very shy, but why is he afraid to talk to strangers? why后面不是应该跟陈述句 I think _______ a foreign language is not easy.You should _______ it often.A.to learn ; to practice B.learning; practice C.learn; practicing D.learns; to practice 正确答案是B,可是think后面不是应该＋to do sth.么 yunnan is a beautiful place for...yunnan is a beautiful place for people _______ (visit)老师给的答案是to visit,但是填visiting对吗?它不是it's+adj+n+for sb to do sth的结构啊,for是介词后面的动词应该加ing吧 there is a good place后面+to do还是doing? he is ready to do sth 中he is a man不是己经是个句子了么 为什么后面直接加了ready啊 what did he后面为什么是加used to do不是use to do be动词(is,are...)后面,什么时候+doing,什么时候+to do如题~我认为是一样的,但应该不对吧.我的意思是.例如:my hobby is drawing/to draw pictures.怎么区分,应该用哪个?