美国GMAT考试中，会把用which指代前面整个主句的定语从句判为错误的语法应用，这种句子该怎么样改?
新东方的《GMAT 语法改错精解》一书讲到，美国GMAT考试中，会把用which指代前面整个主句的定语从句判为错误的语法应用，譬如书中例句：
He worked in this field for several years, which contributed to his later success.
该书表示，这句话一般语法书上都觉得是对的，而GMAT考试觉得，这种语法应用或许会存在关系代词which指代不明的弊病，所以不倡导用，一般会判错。那样我应该怎么样改写这种句子，才能表达了解呢？谢谢！
是的。这个句子语法书也不觉得存在错误。
He worked in this field for several years, which contributed to his later success.
【翻译】他在该范围工作了数年，这能够帮助他后来的成功。
假如必须要修改，那就把定语从句改成一个并列句。找一个代词指代前文即可。比如：
He worked in this field for several years, and it/this/that contributed to his later success.
