I need a knife to cut the watermelon withWhen I handed the report to John,he said that George was the person {to send it to} 1这两句不定式做什么成分2为什么要加with和to3再例句为什么是做定语呢。I need a knife不是完整的主谓宾了吗。而且第二句的the person是表语。为什么不定式也是表语
问题描述：
I need a knife to cut the watermelon with
When I handed the report to John,he said that George was the person {to send it to}
1这两句不定式做什么成分
2为什么要加with和to
3再例句
为什么是做定语呢。I need a knife不是完整的主谓宾了吗。而且第二句的the person是表语。为什么不定式也是表语
答
1.不定式在句中做定语,不定式作名词/代词的定语时一般位于修饰词之后;
2.如果不定式与这个修饰的名词/代词构成动宾关系,不定式中的动词应是及物动词,若不是及物动词,应加上适当的介词,你举的两个例子正好都是不及物动词,所以需要加上适当的介词；
3.(1)There are some chairs in the park for people to sit and take a rest on
(2)The old man needs a person to talk with