The correct option is
A Navy
During the early years of the 20th century, there was a growing debate within the British Empire as to the role the Dominions would play in defense and foreign relations. Because of the developing naval arms race with Germany, a key part of this discussion focused on naval issues. In Canada, the naval debate came down to a choice between two options: either the young country could provide funds, support, and manpower to the Royal Navy, or it could form its own navy, which could help support the Royal Navy if necessary. After extensive political debates, Canadian politicians chose the latter option.
On 29 March 1909, George Foster introduced a resolution in the House of Commons calling for the establishment of a Canadian Naval Service. The resolution was not successful; however, on 12 January 1910, the government of Prime Minister Sir Wilfrid Laurier took Foster's resolution and introduced it as the Naval Service Bill. After the third reading, the bill received royal assent on 4 May 1910, becoming the Naval Service Act which created a Department of the Naval Service under the Minister of Marine and Fisheries, who also became the Minister of the Naval Service. Hence, Option A is correct. The railway started in 1880 while the army was built in 1855. Air Force was built in 1920. Hence, these are incorrect.