A、In the mid-19th century. B、In 1865. C、In the early 1900s. D、In 1908. A

(22)“The Tube” begun in 1863 as direct response to traffic congestion and was the world’s first underground railway system. Steam locomotives first ran on the Metropolitan Line with air so noxious. It was likened to crocodile breath. (23)Moving mail underground in London also started in the mid-19th century.
In 1861, a private company set up a cast-iron pneumatic tube system. Basically, a steam engine powered a large fan into a narrow tube: carriages were blown one way, then dragged back the other way by suction. Getting into a pneumatic carriage—as some test engineers did—must have been like jumping into a modern four-man bobsleigh. In 1865, the Illustrated London News reported on the launch of a pneumatic line under Euston Station, top-hatted Victorians looking on earnestly at this wonder of the age. But after multiple experiments, it failed to attract investors and in 1908, British Post Office engineers visited Chicago to look at (24)its new freight subway system—a labyrinth of tunnels criss-crossing under the city’s famous Loop for almost 100 kilometers (60 miles).
The British visitors were deeply impressed; the General Post Office—then a government department—decided that it would also go underground and electric; something had to be done to avoid the heavy, largely horse-drawn, London traffic of the early 1900s. The Post Office Railway Bill passed into law in 1913 and tunneling work commenced the following year. Coinciding with the outbreak of the First World War, it would take much longer than expected. Over 1,000 tons of cast iron track had to be laid. (25)When the postal railway line finally opened in 1927, it was evidently a triumph, carrying up to four million letters a day between eight London sorting offices.  
Questions 22 to 25 are based on the passage you have just heard.
22.What was the world’s first underground railway system?
23.When did moving mail underground in London start?
24.How long was the new freight subway system?
25.When did the postal railway line finally open?