Die Lehrer essen Sandwiche
One of the multiple choice questions translated "Die Lehrer essen Sandwiche" as "The teacher eats sandwiches." As it was multiple choice this was the obvious answer, but if I had to transcribe it out how do I know if Lehrer is plural or not? It seems the sentence could also be "The teachers eat sandwiches."
The sentence is in plural. You can see it looking at the article "Die" and the verb "essen". "The teacher eats sandwiches" would be "Der Lehrer isst Sandwiche".