Translation:I want to take the subway to get there.
Yes it is, because you don't often have a choice of subways. In Germany and Japan you might but in Germany you'd always distinguish S-Bahn from U-Bahn and in Japan all the different companies and lines join up into one massive system anyway and typically you don't have an option of which company to take to get to a certain station. Basically we'd never say "a subway" just like we'd never say "a freeway".
We would however say "a bus" or "the bus" and "a train" or "the train" since those can refer to both the individual vehicles and the system they're part of. The individual vehicles in the subway are not also called subways, and that's the difference.
Over here "Subway" recently became a fast food chain. I've never heard anybody call the things they sell subways. They're always sandwiches or rolls. Maybe subs, though that sounds too American to me.
But yeah none of the urban trains in Australia are mostly underground even though some of them have a few underground stations.
Aussies overseas do call them subways or metros though because locals think we're talking about long distance above-ground trains when we just say "train".
So this is the 4th 'error' in this lesson that is due to Duolingo's weird translation algorithms and, as usual, I'll quit and go on to another app that's less maddening. There's a lot that is great and useful in Duolingo, but this keeps me forever on the verge of quitting. Also rules out EVER signing up for Duolingo Plus.