Political dominance belonged to the north. Germany, France, and England had large populations and large armies that made them, in the political and military senses, the masters of western Europe. Organized by the practices known collectively as feudalism1, these kingdoms emerged as powerful states with sophisticated machineries of government. Their kings and queens were the leading figures of the age; their castles and cathedrals stood majestically on the landscape as symbols of their might; their armies both energized and defined the age. Moreover, feudal society showed a remarkable ability to adapt to new needs by encouraging the parallel development of domestic urban life and commercial networks; in some regions of the north, in fact, feudal society may even have developed in response to the start of the trends toward bigger cities. But southern Europe took the lead in economic and cultural life. Though the leading Mediterranean states were small in size, they were considerably wealthier than their northern counterparts. The Italian city of Palermo in the twelfth century, for example, alone generated four times the commercial tax revenue of the entire kingdom of England. Southern communities also possessed urbane, multilingual cultures that made them the intellectual and artistic leaders of the age. Levels of general literacy in the south far surpassed those of the north, and the people of the south put that learning to use on a large scale. Science, mathematics, poetry, law, historical writing, religious speculation, translation, and classical studies all began to flourish; throughout most of the twelfth century, most of the continents best brains flocked to southern Europe.
Which of the sentences below best expresses the essential information in the highlighted sentence in paragraph 3？ Incorrect choices change the meaning in important ways or leave out essential information.

A. In political history, northern kingdoms tried to extend their control during the twelfth century, but the south tapped into the rich treasures it had around the Mediterranean.
B. Political history demonstrates that during the twelfth century, while southern states enjoyed the Mediterranean bonanza, northern countries increased the power of their kings.
C. The political history of twelfth-century Europe shows particularly that northern countries continually tried to expand their rule into the south to profit from the riches there.
D. Political history shows that northern kingdoms were so influenced by the example of Mediterranean wealth that they advanced into other areas.