"Professores bebem vinho."

Translation: Teachers drink wine.

[eenai]

they sure do!!!
Let me tell ya...

[aryabferduzi]

That explains why the students in the last lesson drink wine too

[sammazo]

why is the answer "the professors drink wine" wrong?

[eenai]

because the statement. "Professors drink wine", is not a specific, but a general statement. as in "cab drivers smell" for example. not a specific cabbie, or specific group of cabbies, but cabbies in general (not that they do :P)