Complex sentence: Trains operating on the line, i.e., the C151s, the C651s, C751Bs and C151As, which have been withdrawn from North South Line due to December 15 and 17 train services disruptions.
Split into simpler sentences: Trains operating on the line, i.e., the C151s, the C651s, C751Bs and C151As. The C151As have been withdrawn from North South Line due to December 15 and 17 train services disruptions.