The purpose of using a cause and effect structure is to show why something happened.
The cause and effect text structure is usually used in persuasive and expository writing modes. In other words, when an author provides reasons why something happened, he or she is providing an explanation about what caused an effect. Reasons constitute causes while the event that took place is the effect.
Cause and effect is a common way to organize information in a text.
This is indirect characterization, because the excerpt does not explicitly say he was mad at his grandmother. Instead, it gives an implicit clue that he is via body language.