Задание 17 ЕГЭ, английский язык: Полное понимание информации в тексте

Why was Zinoviev's melody of Vecherny Zvon long believed to be a folk tune?

1)  Because the author didn't write his name in the original copy.

2)  Because it was familiar to people as part of church services.

3)  Because after the Revolution the author was not mentioned.

4)  Because the song was first performed by a children's choir.