It says I must have "a sandwich", not just sandwich. I do not see that this sentence specifically says "a sandwich" You should be able to say "I bought sandwich for lunch"
"I bought sandwich" does not make sense in English. You must use an article here, seeing as "sandwich" is a countable noun. :)
This Turkish will kill me for sure. I start to think that I could get it somehow, but there is no chance. I also wrote without " a ". So help me God to learn this language. :(
I think it's not because of Turkish; as Alex pointed out the English noun "sandwich" needs an article (or the number "one") in singular. I guess you could translate "I bought sandwiches…".
A sandwich is a distinct object and not an uncountable substance such as sugar, flour, or beer. I suppose that "bira aldım" could be translated by "I bought beer", without an article. Sorry, English is not my native language (as you will have guessed).
For this sentence, the correct answer is translated as ''I took sandwiches for lunch.'' But ''sandwiches'' are plural in English ... in Turkish plural is sandviçler...
The proposed answer is “I bought a sandwich for lunch,” so singular should be okay. As far as I understand the indefinite Turkish object can mean singular as well as plural. If you want to emphasize singular you can put a “bir” (…bir sandviç aldım).