<p>Try this trick - would you use “they” or “them” in the sentence? “Many of THEM were skeptical of traveling underground.” If “them” sounds right, then it should be “whom.” If “they” had sounded correct, then you would use “who.” That’s how I figure out which word to use.</p>
@someonescarlett Because “Brightly lit stations welcomed the public” is a full sentence and “Many of them were skeptical of traveling underground” is a full sentence. Two full sentences stuck together with just a comma is not correct. You must separate them with a period (“Brightly lit stations welcomed the public. Many of them were skeptical of traveling underground.”), semicolon (“Brightly lit stations welcomed the public; many of them were skeptical of traveling underground.”), or comma/conjunction combo (“Brightly lit stations welcomed the public, but many of them were skeptical of traveling underground.”).