Cities of Western Germany (LL Season Prep) by Abhi

Question 7

Many German cities have an underground rapid transit network known as the untergrundbahn, or "U-bahn." Car lovers and Kraft werkers will already be familiar with the "Autobahn" highway system. What is the similarly named system of regional or commuter rail systems serving most urban areas in Germany--including several interlaced ones along the Rhine river? Full name or abbreviated will do.

S-bahn or Stadtschnellbahn