"우리는 수저를 차렸습니다."
Translation:We set the spoons and chopsticks.
Because the spoons and chopsticks are in this case plural. Therefore, a spoon is grammatically incorrect, especially because it wasn't an option. I think they are saying that they are setting a table, for more than one person, and so it would make no sense to set a spoon. I hope this made sense and was helpful.
From the notes
All Korean speech levels are formed from the 아/어 form we learned in Casual. We then add ~ㅆ to the end of the syllable, giving us 았/었 as the basic past tense verb stem. Vowel harmony ends here, and the double ㅅ is followed by the vowel 어.
There are a number of instances where in English we would use present but in Korean the past. Here we have 생기다 and 오래되다.
In both these cases, these verbs describe something that has already happened. With exact translation, rather than saying "someone is ugly" Korean translates as "someone was poorly formed" and instead of "something is old" Korean has "something has become old."