Question: Which is airport is located in German and second busiest airport in Germany and operates a dense domestic and European network as a member of Lufthansa Cityline? 
Sentence (from "Lufthansa CityLine"): It is a wholly owned subsidiary of Lufthansa and maintains hubs at Frankfurt Airport and Munich Airport, from where it operates a dense domestic and European network as a member of Lufthansa Regional.
Relevant evidence: No