选择下列段落正确的拓展方式Many old buildings in cities are still being found useful. In several cities, old buildings that wereno longer being used have been converted to a variety of useful structures. For example, oneschool building was changed into ninety nine rental units for elderly and low income residents. InBaltimore, Maryland, six schools were converted into 132 units with the help of a four milliondollar city bond financing arrangement. “School House 77” in Boston utilizes three recycledelementary schools and an abandoned instrument factory. All these examples show how cities are using unneeded schools, police stations, libraries, and boarded up factories that are structurally sound and even architecturally interesting buildings.

A. Development by example
B. Development by space
C. Development by classification
Development by comparison and contrast