It's got to be NPN. I'll tell you how I reached that conclusion.
Emitter of the 2SC3205 is connected to the emitter of the unknown transistor. So, it's an NPN transistor, whose emitter and the emitter of the 2SC3205 are connected to a common point - ground.
The collector is connected to the -ve terminal of the buzzer. If it was a PNP transistor, the collector would be connected to the +ve terminal of the buzzer. If instead, the -ve terminal of the buzzer and the collector were grounded (in which case, it could have been a PNP transistor), the base should have had a pull-down (or pull-up) resistor, which it doesn't have.
And you checked the common emitters are connected to ground. So, that proves that it is an NPN transistor.
Hope this helps.
Tahmid.