[填空题]If by "suburb" is meant an urban margin that grows more rapidly
than it already developed interior, the process of suburbanization began 41______
during the emergence of the industrial city in second quarter of 42______
the nineteenth century. Before that period the city was a small highly
compact cluster which people moved about on foot and goods were 43______
conveyed by horse and cart. But the early factories built in the 1840’s
were locating along waterways and near railheads at the edges of cities, 44______
and housing was needed for the thousands of people drawn by the prospect
of employment. In time, the factories were surrounded by proliferating
mill towns of apartments and row houses that abutted the older, main cities.
As a defense against this encroachment and to reduce their tax bases, 45______
the cities appropriated their industrial neighbor. In 1854, for example, 46______
the cit