The boy to write this letter needs a pen.的词法与句法

The boy to write this letter needs a pen.的词法与句法 The boy (writes/to write)the letter needs a pen.为什么用to write 老师,请问英语中在什么情况下使用不定式?比如"The boy to write this letter needs a He needs a pen to write ( ) The little boy needs a blue pen 里的表语? Write a letter to pen friend saying can you write this letter for me with a pen? write a letter to your pen friend in the USA to tell them th The boy in the classroom needs a pen of yours的定语是什么? Write a letter to Sam to ask him to be your pen pal 的中文是什么? Write a letter to ask for a pen pal write a letter to ask for a pen