In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.
Q: Question: Which of the lines that uses the A-series trains began first? Passage:NSB Class 73 () is a class of 22 electric multiple units built by Adtranz for the Norwegian State Railways. The four-car trains were modifications of Class 71, which was again based on the Swedish X2. The A-series consists of 16 intercity trains; they were delivered in 1999 and 2000 and are used on the Bergen, Dovre and Sørland Lines. The intercity service was branded as Signatur until 2003. The B-series consists of six regional trains delivered in 2002 and used on the Østfold Line. The regional trains were originally part of the Agenda concept. The trains have a power output of and a maximum speed of . They have an overall length of and have a capacity for 208 seated passengers in the A-series and 250 in the B-series. The trains have a tilting mechanism allowing for faster travel through curves.

A: 
The A-series consists of 16 intercity trains; they were delivered in 1999 and 2000 and are used on the Bergen, Dovre and Sørland Lines