Which of the following is a run-on sentence?
Its ice slab walls of thick stone lie dormant, awakening only to sing the organ’s echoing melodies that reached my apartment window on Sunday mornings.
The city center in the valley below holds a 13th century cathedral with piercing Gothic spires that stretch upwards toward the heavens.
From its towering position on a hill overlooking the valley, a castle fortress rests; this silent sentinel stands as a powerful reminder of the ancient kings and queens who ruled centuries past.
The melodies would blow through my window with the breeze their notes would bounce off the walls and ceiling.