In a single game against married, Juan is looking at Carmen and Carmen is looking at David. Juan is married and David is single.
Is there a married man looking at a single person?
c) It cannot be determined with certainty
Since you can only be married or single we have 2 possibilities for Carmen:
Option 1 -> Carmen is single. In this case, since Juan (married) looks at Carmen (single) the answer is YES
Option 2 -> Carmen married. In this case, since Carmen (married) looks at David (single) the answer is also YES
Therefore, whether Carmen is married or single, There is ALWAYS a married man looking at a single.