Cấu trúc: S + was/were + V-ing + O I was studying at 8 p.m. yesterday. They were playing football when it rained. Was vs Were: WAS: I, he, she, it WERE: you, we, they I was reading. She was sleeping. You were waiting. They were talking. While vs When: While + Past Continuous (hành động dài) When + Past Simple (hành động ngắn) I was reading while she was cooking. When I arrived, she was sleeping.