I was singing last night. 昨晚我在唱歌
He was playing basketball this afternoon. 下午他在打篮球
Mary was watching TV on Saturday evening. 周六晚上玛丽正在看电视
They were looking at the birds. 他们当时正在看鸟儿
Tom was sleeping when you called him. 你给他打电话的时候他正在睡觉.