To maintain parallel structure across all sentences, the best revision is:
Sentence 1 should be revised to read, “Outside, the snow fell; inside, the heater came on with a distant roar.”
This revision aligns the structure of Sentence 1 with the others, as they all begin with "Outside" followed by an action, and "Inside" followed by another action. The other sentences already maintain this structure.
Here's the corrected version of all sentences for clarity:
- Outside, the snow fell; inside, the heater came on with a distant roar.
- Outside, the wind howled through the big oak; inside, a log snapped in the fireplace.
- Outside, footsteps crunched hurriedly past the window; inside, the cat stretched and purred.
- Outside, an owl hooted softly; inside, a page turned.