Er... the time signature? If you have to ask, then I'm guessing you don't know what a time signature is, so I suggest you should look it up before your teacher starts asking difficult questions about it.
Go with Naz. What you should be looking at is the upper number, which tells you how many of the beats there are in a bar. The lower number tells you what sort of note value each beat is - a minim, crotchet, quaver or whatever.
If you're American (I notice you say 'measure' and not 'bar'), then, for instance, 3/4 = 3 quarter notes (crotchets), to the bar; 2/4 = 2 quarter notes; 2/2 = 2 half notes (minims); 6/8 = 6 eighth notes (quavers) etc etc.