作定語的成分
不定式作定語：
The boy to write this letter needs a pen./寫這封信的男孩需要一支鋼筆.
分詞（短語）作定語：
The smiling boy needs a pen bought by his mother./那個微笑的男孩需要一支他媽媽買的鋼筆.
The pen bought by her is made in China./她買的筆是中國產(chǎn)的
動名詞作定語：
the girl sitting under the tree is my sister
請問在什么情況下用什么作定語,