Definition: Given a paragraph, your job is to generate a question that can be answered from the passage. The answer to your question should be a single entity, person, time, etc. that can be extracted from the passage.
Input: There are also several smaller freight operators and numerous tourist railways operating over lines which were once parts of a state-owned system. Victorian lines mainly use the 1,600 mm (5 ft 3 in) broad gauge. However, the interstate trunk routes, as well as a number of branch lines in the west of the state have been converted to 1,435 mm (4 ft 8 1⁄2 in) standard gauge. Two tourist railways operate over 760 mm (2 ft 6 in) narrow gauge lines, which are the remnants of five formerly government-owned lines which were built in mountainous areas.
Output:
What is the gauge of the Victorian rail lines?