This task is about reading the given passage and construct a question about the information present in the passage. Construct a question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) its answer is a continuous text span from the paragraph. Avoid creating questions that (i) can be answered correctly without actually understanding the paragraph and (ii) uses same words or phrases given in the passage.

[Q]: After 1870, the new railroads across the Plains brought hunters who killed off almost all the bison for their hides. The railroads offered attractive packages of land and transportation to European farmers, who rushed to settle the land. They (and Americans as well) also took advantage of the homestead laws to obtain free farms. Land speculators and local boosters identified many potential towns, and those reached by the railroad had a chance, while the others became ghost towns. In Kansas, for example, nearly 5000 towns were mapped out, but by 1970 only 617 were actually operating. In the mid-20th century, closeness to an interstate exchange determined whether a town would flourish or struggle for business.
[A]: after about what year did railroads bring hunters to the great plains?


[Q]: Mean speeds vary greatly, but is typically around 1 m (3 ft) per day. There may be no motion in stagnant areas; for example, in parts of Alaska, trees can establish themselves on surface sediment deposits. In other cases, glaciers can move as fast as 20–30 m (70–100 ft) per day, such as in Greenland's Jakobshavn Isbræ (Greenlandic: Sermeq Kujalleq). Velocity increases with increasing slope, increasing thickness, increasing snowfall, increasing longitudinal confinement, increasing basal temperature, increasing meltwater production and reduced bed hardness.
[A]: In what area of Greenland can glaciers move 20-30m per day?


[Q]: Britain was concerned about Russian activity and Sir John Burgoyne senior advisor to Lord Aberdeen urged that the Dardanelles should be occupied and throw up works of sufficient strength to block any Russian move to capture Constantinople and gain access to the Mediterranean Sea. The Corps of Royal Engineers sent men to the Dardanelles while Burgoyne went to Paris, meeting the British Ambassador and the French Emperor. The Lord Cowley wrote on 8 February to Burgoyne "Your visit to Paris has produced a visible change in the Emperor's views, and he is making every preparation for a land expedition in case the last attempt at negotiation should break down.":411
[A]:
Who was concerned with Russia  capturing Constantinople?