Being very dark, (1)/ the visitors found it difficult (2)/ to locate the switch. (3)/ No error (4)

Answer

1

Explanation

It beingvery dark will replace beingvery dark This is an error of Unattached subject/Participle A Participle mustmodify the Subject of the sentence.
A Participle mustmodify the Subject of thesentence.
Having bitten the boy, the farmer killed the snake
Having bitten the boy , the farmer killed the snake.
This sentence means that it was the farmer who bit the boy and not the snake. It should be , therefore rewritten as
The snake having bitten the boy , the famer killed it .