Final answer:
The top ten newspaper chains controlled approximately 70% of the total newspaper circulation in the U.S by the early 2000s.
Step-by-step explanation:
The top ten newspaper chains controlled > 75% of the total newspaper circulation in the U.S by the early 2000s.
According to the information provided, newspaper chains owned by corporations accounted for over 80% of circulation. So, it is likely that the top ten newspaper chains would have a significant share of the total circulation, which is represented by option C) 70%.
However, since the information does not specifically state the exact percentage controlled by the top ten newspaper chains, option C) 70% provides the closest estimate based on the given information.