Final answer:
The mode in this histogram is 45 minutes.
Step-by-step explanation:
The mode is the value that appears most frequently in a data set. To find the mode in a histogram, you need to identify the bar that has the highest height. In this case, the bar with a height of 45 represents the amount of time Mr. Crawford's students spent on homework the most. Therefore, the mode is 45 minutes (option a).