Final answer:
The modern continents began to take shape around 650 million years ago, during the Paleozoic Era with the formation of Gondwana, leading eventually to the configuration we see today. The correct option is C.
Step-by-step explanation:
The question relates to the time period when the modern continents began to take shape. According to geological history and the concept of plate tectonics, this process of the continents forming into their modern positions can be traced back to the breakup of the supercontinent Pangaea.
Pangaea itself began to break apart about 200 million years ago, which eventually led to the separation and formation of the Atlantic Ocean. Before Pangaea, there were other configurations of continents including the formation of Gondwana during the Paleozoic Era, around 550 million years ago.
Based on the provided options and geological time scales, the correct answer to when the modern continents began to take shape is C. 650 million years ago. This is the time frame during which Gondwana formed, an essential step towards the configuration of continents as we know them today.