The correct answer is: D. 1933
The new Harbour rail line was inaugurated on 15 December 1933. It was built to connect the city of Sydney with the newly developed suburbs of North Sydney and Manly. The line was built by the New South Wales Government Railways and was designed by the engineer John Bradfield. The line was originally electrified at 1500 volts DC, but was later converted to 25 kV AC. The line is now operated by Sydney Trains.
Option A is incorrect because the new Harbour rail line was not inaugurated in 1925. The line was not even under construction in 1925.
Option B is incorrect because the new Harbour rail line was not inaugurated in 1928. The line was not even under construction in 1928.
Option C is incorrect because the new Harbour rail line was not inaugurated in 1931. The line was not even under construction in 1931.