It can be both.
Mae hi'n dod ar y bws nesa = She's coming on the next bus.
Dw i'n byw drws nesa = I live next door.
there was no sound so I could not hear the word. that has happened to several of the sounds that we are supposed to hear and then type in the box
Unfortunately this is an internal glitch of Duolingo which we cannot control (we also can't choose which sentences appear as 'write what you hear' sentences), so we have to wait for Duolingo to solve the glitch.