upitan

1. questionable; doubtful
   Njegovo učešće u utakmici je još upitno. — His participation in the match is still in doubt.
   Kvalitet tog proizvoda je prilično upitan. — The quality of that product is rather questionable.
2. (of a look, tone) questioning; quizzical
   Pogledala me je upitnim pogledom. — She gave me a questioning look.
3. (in grammar) interrogative
   Upitna rečenica završava se upitnikom. — An interrogative sentence ends with a question mark.

In the sense "doubtful" it is mostly used after biti: to je upitno.