问几个英语语法问题,1、signal to be careful.这里的signal不是人啊,为什么可以用to be?t

1、signal to be careful。这里的signal不是人啊,为什么可以用to be?to be是不是成为,变为的意思?2、如果我要表达【我不能白送你东西】和【你这种行为是白送我东西,我不能接受!】这两个意思,这里的【白送】如何表达?【我不能白送你东西】=I can't send you anything for nothing =I can not give you anything for nothing to be rewarded =I can not send you anything without any reason /purpose【你这种行为是白送我东西,我不能接受!】=I can't accept the action that you send me things for nothing =I can not accept your action to give me something for nothing to be rewarded /compensated /returned/ acknowledge/ thanked【白送】如何表达=To give something to somebody for nothing reasonable /special 3、I got U,啥意思?为什么用got?这里用过去式想表达什么?I got you,意思,我明白你的意思了,我懂你意思了；是英语口语使用频率最高一个短语。 再问： 第一个没答啊，不好意思，谢谢啊。 再答： 1、signal to be careful。这里的signal不是人啊，为什么可以用to be？to be是不是成为，变为的意思？ 为动词不定式做后置定语修饰 SINGAL ,意思，需要小心信号，暗号，或者导火线