The passage explicitly states that deep reading requires not just time, but also other factors, indicating that while time is a significant component of deep reading, it is not the sole requirement. This makes option C the most accurate reflection of the passage's suggestion. Options A and D are incorrect because they either underestimate the time required or overemphasize time as the only factor. Option B, while partially correct in suggesting a correlation between time and comprehension, does not fully capture the passage's emphasis on the necessity of additional factors beyond time for deep reading.