This is the factory _where/in which___ makes toys for children.
This is the factory __where/in which__ we worked 3 years ago.
This is the factory __which/that__ we visited last year.
This is the factory __where/in which__ I spent 10 years.
Oct,1,1949 was the day __when__ the P.R.C was founded.
Oct,1,1949 was the day ___when_ I saw the rising of the 5-star flang
Oct,1,1949 was the day __which/that__ we spent together
Oct,1,1949 was the day __which/that__ I'll forever remember.
答案滿意吧.