The earlier type of suburb,which was most dependent on the r

The earlier type of suburb,which was most dependent on the railroad,had a special advantage that could be fully appreciated only after it had disappeared.These suburbs,spread out along a railroad line,were discontinuous and properly spaced; and without the aid of legislation (法规) they were limited in population as well as area; for the biggest rarely held as many as ten thousand people,and under five thousand was more usual.In 1950,for example,Bronxville,New York,a typical upper-class suburb,had 6,778 people,while Riverside,Illinois,founded as early as 1869,had only 9.153.
26.What was the special advantage of the old type of suburb?
A) Its nearness to the railroad.
B) The vastness of its open space.
C) Its small size in area and population.
D) The high social status of its residents.
为什么不选A?