According to the "person by situation" approach,

A) personality is more important than the situation in determining behavior.
B) there is little evidence for cross-situational consistency.
C) behavior is determined by an interaction of personality and the situation.
D) personality researchers need to measure behavior in more than one way.

According to the "person by situation" approach, behavior is determined by an interaction of personality and the situation. This approach emphasizes that both traits and situation play a role in determining behavior, and that behavior can vary depending on the situation. Therefore, option C is the correct answer. Option A is incorrect because it suggests that personality is more important than the situation in determining behavior, which is not necessarily true. Option B is also incorrect because there is evidence for cross-situational consistency, although it is not perfect. Option D is partially correct, but not the best answer, as this approach is concerned with how traits interact with situations, rather than how to measure behavior in different ways.