Informal language, spontaneity, formality, and intensity are characteristics of:

The characteristics of informal language, spontaneity, formality, and intensity align well with interpersonal communication. Interpersonal communication is typically characterized by direct, face-to-face exchanges between individuals. In such settings, the use of informal language allows for a more personal connection, helping to convey emotions and attitudes effectively. Spontaneity reflects the dynamic nature of these interactions, where responses and dialogue can flow naturally without premeditation.

Formality in interpersonal communication can vary greatly depending on the context and relationship between the participants, which adds depth to communication styles. Intensity, referring to the emotional weight or energy behind a message, is also a critical aspect as it influences how the message is received and perceived by the other party.

In contrast, the other options focus on different aspects of communication or educational contexts. Skills mastery generally involves a more structured and formal approach to acquiring skills. Informal education refers to learning that occurs outside traditional educational environments and may not emphasize the same interactive qualities. Transmitted communication is often more one-sided and lacks the immediacy and personalized engagement characteristic of interpersonal communication. Therefore, the defining features of interpersonal communication make it the appropriate choice in this context.