To determine how long it will take the train to travel 525 miles at a speed of 150 miles per hour, you can use the formula:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]
Plugging in the values:
\[ \text{Time} = \frac{525 \text{ miles}}{150 \text{ miles per hour}} = 3.5 \text{ hours} \]
Therefore, it will take the train 3.5 hours to travel 525 miles. The correct answer is 3.5 hours.