Read the passage below and decide which option A, B, C or D best fits each space from 19 to 23

                The railway system in Viet Nam was first built in 1899, when Viet Nam was still a French colony. The total (19)_____ of the railroad is over 3,000 km, with the main route being the North-South (20)______, which is 1,726 km long. This track was considered the backbone of Indochina at the time. Now, the rail system covers 35 out of the 63 cities and provinces of Viet Nam.

However, the system was (21)______ damaged by bombings during the war. In 1975, after the reunification of the north and the south, the Vietnamese government decided to restore the system. In the space of a year, hundreds of bridges, tunnels, and stations were restored, along with 660 km of tracks. The new and improved system was (22)______ the Thong Nhat Express. Thanks to the rail system, travelling from north to south has become much more convenient for tens of thousands of people.

In the past, in order to be able to buy train tickets people had to wait in long lines. Now, (23)______ can buy tickets online, or at the central station, without having to wait that long.

The total (19)_____ of the railroad is over 3,000 km,