I worked for a factory which produced cars

问到了。。- -
Jack is working in the factory (which) his father visited yesterday
其中的visit可以和之前的factory连起来用
一般遇到这种问题，你就要注意看，后面的结尾是否可以与前面所修饰的词语通顺地连起来读。如果能组成一个通顺的句子，就用which/that，不能就用where、what、when等

（真是的我连这么重要的东西都忘了。。罪过罪过。。）
我的Q是：378065806

produced cars不是完整的句子，缺主语，所以用which.
his father visited yesterday 这里缺宾语，所以要用that.

总之就是缺不缺成分的问题，你Q多少？加了慢慢说。

这其实是一个定语从句中关系代词、关系副词的使用问题。当先行词是表地点的名词时，可用 which 、that也可用where，关键看关系词在定语从句中的作用。当关系代词在从句中作主语或者作宾语时，可用 which 也可用that，如I worked for a factory which produced cars 句中所用，which在从句中作主语。而Jack is working in the factory (that) his father visited yesterday 中that 在从句中作宾语。但当关系代词前有介词时，就只能用which 了。
当关系词在从句中作地点状语时，只能用关系副词where，如Jack is working in the factory where his father has worked for 25 years 句中的where在his father has worked for 25 years 中做状语。