The best example of a central idea among the options provided would be "Knowledge can be a power mover of change."
This statement encapsulates a broader concept, suggesting that acquiring knowledge can lead to significant transformations in various contexts—such as personal growth, social progress, or technological advancements. While "change can be a difficult process" highlights the challenges associated with change, it is more of a secondary observation rather than a central theme. Knowledge as a catalyst for change implies agency and potential, making it a more compelling central idea.