Characters within a story often change. Sometimes, it is one event, conversation, or obstacle that has been overcome that changes a characters outlook about a situation.
Other times, it is the accumulation of several events that makes a character think about a situation or even himself differently. Comparison and contrast is such a broad skill that it also encompasses the comparison and contrast of characters.
It is important for students to not only state the fact that a character has changed, but also identify and explain the plot events that led to this change.