Gloom brings a sentiment of melancolia and darkness. Combined with frightening, we have a very unique description. We something must be shadowy and frightening to fit. We have darkness which can substitute gloom in one of its definitions, and scary which certainly substitutes frightening quite well.
The sentence that contain simple subject would be : C. The rain came down in the sheets A Simple subject is basically a subject that doing the action. In this case, the rain is doing 'came down'
