The song in the play cannot be deleted it is ____ to the story.

The correct answer is -D.

The meaning of integral is elementary, fundamental, anything which is not omittable, removable.

The sentence implies here that song in that play is not removable as it is part of that story or it is fundamental to story.

Meaning of remaining options

1)Intervene- to come between.

2)Innate- Inborn,natural.

3) exacting- demanding, requiring precise accuracy.

If we go through the options only `Integral' best fits into the blank.