Final answer:
Behavioral leadership theory focuses on the importance of a leader's behavior, including interpersonal skills, in determining leadership effectiveness.
Step-by-step explanation:
The theory that emphasizes that leadership effectiveness is contingent upon the executive nurse's interpersonal skills is the Behavioral leadership theory. This theory suggests that leaders are most effective when they are able to exhibit a certain style of behavior that matches the needs of the situation at hand. Within the realm of leadership theories, the Behavioral leadership theory stands out by focusing on the actual behaviors and styles that make leaders effective in various situations.