what when why how

Câu hỏi :

In the 1960s, The Beatles were probably the most famous pop group in the (1) _____world. Since then, there have been a great many groups that have (2)____  enormous fame, so it is perhaps difficult now to imagine (3) ____ sensational The Beatles were at that time. They were four boys from the north of England and none of them had (4)______ training in music. They started by (5) _____ and recording songs by black Americans and they had some success with these songs. Then they started writing their (6) ______ songs and that was when they became really (7) ____. Beatles changed pop music. They were the first pop group to achieve great (8) ____ from songs they had written themselves. After that it became common for groups and singers to write their own songs.