[Grammar] Singular / Plural - Students must bring their umbrella(s) or raincoat(s)

Which one is correct?
1. Students must bring their umbrella or raincoat.
2. Students must bring their umbrellas or raincoats.
Thanks!
Delphine

You can hear both. I prefer 2 myself.

To be honest, I can't imagine a context where someone must bring umbrellas. Probably, "should" sounds better.
Not a teacher nor a native speaker.

Boris Tatarenko said:

To be honest, I can't imagine a context where someone must bring umbrellas. Probably, "should" sounds better.

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The students might not be allowed on the field trip if they don't bring their umbrellas. In that sense, they must bring them (if they want to go on the trip).