People were alarmed___ by ___the tiger. "By" is the only preposition that works for me. I suppose " for " could work, if they are trying to protect a tiger and they see a lot of poachers entering the tiger's territory.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
AlpheccaStars"Alarmed at" is a very old-fashioned collocation. It might still be in common use in Indian English which tends to retain these old forms.Oxford Advanced Learner's Dictionary has it: