Social desirability scales measure the extent to which a person

A) possesses socially desirable characteristics.
B) understands the rules of social interaction.
C) tries to present himself or herself in a favorable light.
D) is able to understand the meaning of the test items.

Social desirability scales measure the extent to which a person tries to present himself or herself in a favorable light. This means that they may not necessarily possess socially desirable characteristics, but try to present themselves as if they do. Understanding the rules of social interaction or being able to understand the meaning of test items may be important in some contexts, but they are not directly related to social desirability scales.