Chia các động từ trong ngoặc ra thì simple past hoặc present perfect: 1.We (studied)......a very hard lesson the day before yesterday...... 2.We (have studied)..........almost every lesson in this book so far ........ 3.We (have never watched) .........that television program....... 4We( watched) ........an interesting program on television last night.... 5 My wife and I ..........(had travelled) by air many times in the past Giúp mình với