In the Arrow I just flew for my CPL, the aerials were arranged:
Cockpit roof: chevron-shaped glideslope aerial
Towards back of cabin: VHF Radio aerials
Top of tail: VOR aerials (shaped in a V)
Undernearth, just behind nosewheel: Transponder (short with a ball on the end)
Underneath, just in front of wing: DME
Underneath, half way between wing and tail: ADF
Underneath, near tail, Marker
There seems to be quite a wide range of radio set-ups for Arrows, so don't take any of our descriptions as gospel for your particular aircraft.
My school provided me with a diagram of the aerial layout. The undercarriage and airframe are detailed in the POH as I recall. It's unlikely that the examiner would ask you anything that isn't in the POH.
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