difficult to fly还是difficulty to fly.fly不是动词么 副词修饰,为什么答案是形容词

to fly I saw a bird fly to the north fly ing 是还是 fly They fly uninvited into our rooms ``` fly 在这里是动词 后面的形容词怎么能修饰 不是副词修饰动词吗?为什么是you have to be careful? careful不是形容词吗? we fly kites. 为什么fly 是动词原形,谢谢 it's a good day to fly our kites.为什么用to fly?是不定式吗? 我想飞 的英文说法?是 I WANT FLY 还是 I WANT TO FLY fly fly. Learn to Fly 歌词 hope to fly Ready To Fly 歌词