"The tourists did not even ask if they could smoke."
Translation:Ti turisti se ani nezeptali, jestli můžou kouřit.
A simplified rule: Czech has a strong tendency to use the simple demostrative pronouns (i.e. "TEN" and its forms, rather than "tento", "tamten" or others) in places where English uses the definite article IF the definite article in English can be replaced with an indefinite article (or zero-article in plural) to change the meaning. Therefore:
- Tourists didn't ask. - Turisti se nezeptali. (some tourists, nějací turisti)
- The tourists didn't ask. - Ti turisti se nezeptali. (specific tourists defined by context or previous sentences)
It is still possible to leave out the demonstrative here and just say "turisti" for "the tourists". It's also accepted in this exercise. It's just not commonly done in practice. We normally add demonstratives in these situations - some say this is a German influence on Czech (and Slovak, to a lesser extent), since other Slavic languages do it noticeably less (except Bulgarian which has full-fledged definite articles).
Be aware though that most definite articles in the English language are there only for the sake of grammar and not to actually distinguish between "some" and "specific" entities (like the two bold "the" in this very sentence). These are not "translated" as demonstratives, they serve no purpose from the point of view of Czech.
One can often omit the demonstrative if it is clear who you mean when you say "turisti".
If there is a single group of tourists around and we know about them and perhaps even discussed about them before. It is possible to just say "turisti" and we know that they are "the turists" that are over there.
Similar thing was to be met in the introductory lessons with animals.
Pes žere myš. - A dog is eating a mouse.
But if there is only one dog around and we know which dog we are speaking about if we just say "pes" - like if we just have one dog ... then it can also mean:
The dog is eating a mouse.
This also works if there is one clear "the dog" in the story you are telling or just one dog in the painting you are describing.
Note that it really strongly depends on the language feel of the native speakers of the language. I already mentioned that in Russian you use demonstrative much less. Russian would really use just "turisti" and just "pes", no demonstrative would have been used in the sentences discussed.
And there is no strict logic to be searched in these differences, it is just the language feel you have to develop.
"Turisti se ani nezeptali, jestli můžou kouřit." is definitely among accepted answers, it shows green (valid) when I test it. Perhaps you had another mistake in there somewhere. It's good to use the report button in these situations as we can then see what you entered.
Here the english article works the same as a demonstrative. Nothing changes much if you use "Those tourists" instead. The English article here points to some specific tourists and is not simply dictated by grammar as in "the first", "the last"...
Czech simply does not have any articles. This grammar feature is missing in Czech. Still, Czech uses demonstratives reasonably often. Much more often than Russian, for example.
So it is not possible to mechanically translate English articles and demonstratives, one must follow the conventions of the target language. Even Slavic languages do differ among themselves a lot.