"Which boys were here yesterday?"
Translation:Kteří chlapci tady včera byli?
Why was I told I had a wrong word when I used a different order? (Kteří chlapci byli tady včera)
- The verb být should go to the second position if it is used as an auxiliary verb. This is not the case, here.
- The goal of duolingo (and the mods) is not to award us points, but to teach us correct Czech. When a learner proposes a sentence that sounds awkward, it is good to make him/her aware of that - even if the proposed sentence seemingly follows all available rules.
You are correct. It is important to pay attention to the distinction between the past tense and conditional auxiliary být on the one hand and the regular copula být on the other. Eventually the student even needs to recognize that the present positive copula is different from the negative and/or the past copula. It may be asking a lot, but to the extent we do not want to sound like Yodas, it is a necessary pain. More details here: https://forum.duolingo.com/comment/38369227
Put "tady" in the second position: "Kteří chlapci tady byli včera?" or "Kteří chlapci tady včera byli?"
OR put it at the end to stress it: "Kteří chlapci byli včera tady?" or "Kteří chlapci včera byli tady?" - these two are accepted, but they're a lot less common than the first two versions.