Four statements are given below at A, B, C and D. There may be some errors in the given statement(s). The incorrect statement is your answer.

• Many Japanese cities had extensive tram systems until the 1960s, when increased motorization started to make some lines disappear.
• Increased motorization started to make some lines disappear after the1960s until when many Japanese cities had extensive tram systems.
• When increased motorization started to make lines disappear, many Japanese cities have extensive tram systems until the 1960s.
• Until the 1960s, when increased motorization started to make some lines disappear, many Japanese cities had extensive tram systems.