有两个词组 travel to the USA travel all over the world 请问travel 后

有两个词组 travel to the USA travel all over the world 请问travel 后面要不要加to
另外,以may Must Need 开头的问句相对应的肯定回答和否定回答分别是什么 xiexie
travel all over the world为什么不加to?初二英语里must 肯定 must 否定needn't ;Need 肯定must 否定needn't ; may 肯定 can 否定can't

travel all over the world 这里‘travel’是一个及物动词所以不用加‘to‘
travel to the USA 里的‘travel’是不及物动词,后面必须加一个介词.
情态动词
may:----yes,you must
----no,you can't
must:做推测讲译为“一定”
---yes,he must
---no,he can't
做必须讲译为“必须”
---yes,you must
---no,you needn't
must:
肯定must（必须）,否定must not/mustn't/needn't（不准,禁止）He mustn't be there 他一定不在那儿.Mustn't I smoke here?禁止在这儿吸烟吗?you mustn't smoke here.你不能在这儿吸烟.
注意,must 的否定也有用needn't的.Must I finish the work this morning?Yes,you must/No,you needn't.我必须早上就完成工作吗?是的,必须/不,不需要.
need:
肯定need(需要/必须),否定needn't.You need not go yet ,need you?Yes,I must/ I need to/ I have to/No,I needn't或者 No,I don't have to.你不一定要去,是吗?是的,我一定要/必须/不得不去/不,不一定要去.
shall(只和第一人称连用 we/I):
肯定shall（将/必将/可以/.好吗）,否定 shall not.注意,当回答中主语不再是第一人称,Shall要变成should.Shall I go to school?Good idea/Yes,you should./No,you shouldn't.但是回答主语仍旧是第一人称时,shall 不用变.Shall we go to school?Yes,we shall/No,we shall not/I'd love to,but I can't.
may:
肯定may(可以/许可/能),否定may not.注意过去式,虚拟语气或客气是用might/mightn't.May I close the window?Yes,go ahead/Yes,you can（一般不这么说）/No,I'm afraid you may not.