Вставь is или are
This story about historical events...boring
Books about animals....interesting 
My favorite book..."Treasure island".
It...about adventures.
Comics...fun
Fairy tales...stories about magic things

Всё просто. Когда множественное число - are, когда единственное - is.

Спасибо!

This story about historical events is boring.Books about animals are interesting.My favorite book is "Treasure island".It isabout adventures.Comics are fun.Fairy tales are stories about magic things.

1) is2) are3) is4) is5) are6) are