In character development, which aspect involves understanding characters' strengths and weaknesses?

The correct choice is script analysis. This process involves a deep examination of the text to uncover the motivations, backgrounds, and psychological aspects of characters. By engaging in script analysis, actors gain insight into their characters' strengths and weaknesses, which is crucial for developing a nuanced performance. Understanding these aspects allows performers to portray their characters authentically, responding dynamically to the script's demands and the relationships with other characters.

Blocking, while important in terms of physical movements on stage, does not directly address character psychology. Costume fitting is focused on the visual representation of a character and does not delve into their internal traits or emotional layers. Acting exercises are mainly designed to improve performance skills but may not specifically target the strengths and weaknesses of characters as clearly as script analysis does.