she bought me a pen yesterday→I（）（）（）（）yesterday

she bought me a pen yesterday→I（）（）（）（）yesterday
she bought me a pen yesterday→I（）（）（）（）yesterday

she bought me a pen yesterday→I（）（）（）（）yesterday
she bought me a pen yesterday→I（was）（bought ）（a）（pen ）yesterday
加油!不明白再问!如果帮到你,请采纳,谢谢!

buy 是加双宾语的动词，因此buy sth. for sb. = buy sb. sth. 给某人买某物
he bought me a pen yesterday
变成被动就是
I was bought a pen yesterday。

原句是主动句，改成被动句
she bought me a pen yesterday→I（was）（bought ）（a）（pen ）yesterday。