找出下列句子的一處語法錯誤：
When a serious pollution problem has been created by a factory, which representing a health threat to citizens, it is also advisable to turn to the government for help.
♜ 適用考題：
Most people can solve important problems in their lives by themselves or with the help of their families; help from the government is often unnecessary. (2012.1.8)
答案：
When a serious pollution problem has been created by a factory, which represents a health threat to citizens, it is also advisable to turn to the government for help.
When a serious pollution problem has been created by a factory, which representing a health threat to citizens, it is also advisable to turn to the government for help.
♜ 適用考題：
Most people can solve important problems in their lives by themselves or with the help of their families; help from the government is often unnecessary. (2012.1.8)
答案：
When a serious pollution problem has been created by a factory, which represents a health threat to citizens, it is also advisable to turn to the government for help.