Many #teaching techniques (e.g., Mazur's Peer Instruction) suggest asking a (well-designed) #MultipleChoice question of the class and having them hold up #cards marked A/B/C/D.
... so you'd think someone would be manufacturing such cards. After *several minutes* of searching, pretty much all I can find are PDF templates to print out and cut apart with scissors.
Closest thing so far:
https://cardsfortheculture.com/products/fact-based-a-b-c-d-response-cards
There has to be a way to do this more cheaply. Also, having each letter a different color would make it easier to read the room.
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2ck 
@peterdrake at my uni, we all had to buy these clickers that registered our responses, then the instructor would display them on the board
@2ck Yeah, that can also be done with web services like PollEverywhere.
The clickers are needlessly expensive and even the website is another layer of technology I'm hoping to avoid.