A train authorized by a timetable schedule.

• A. Extra Train
• B. Regular Train
• C. Yard
• D. Siding

Answer: (B)

The key idea here is how trains are classified by schedule. A train that is listed and authorized by the timetable is part of the published, regular service. It runs at the times and along the routes shown in the schedule, so it’s a regular train.

An extra train, by contrast, is run in addition to the published timetable to handle surge demand or special needs, and it isn’t part of the standard schedule. A yard is a facility for storing and sorting cars, not a type of train, and a siding is a track used to hold trains or equipment, also not a train type.

So, the train that matches “authorized by a timetable schedule” is the regular train.