Final answer:
Colonial cities functioned mainly as mercantile centers that collected agricultural produce and distributed imported goods, playing a key role under the mercantilist system. Therefore, the correct option is A.
Step-by-step explanation:
Colonial cities primarily functioned as mercantile centers for collecting agricultural goods and distributing imported manufactured goods. These colonial centers played an essential role under the mercantilist system, fueling the British Empire's success by providing raw materials and engaging in profitable farming due to the richness of the American land and the need for self-sufficiency. Some light manufacturing existed for local markets, though it did not directly compete with English industry. Over time, internal and external trade led to a demand for skilled and unskilled labor in metropolitan areas like Philadelphia and New York, contributing to economic growth and creating a foundation for later industrial expansion.