The second kind of learning is called "operant conditioning." This occurs when an individual learns to do things that produce rewards in his environment and learns not to do things that produce punishments. For example, if a mother always attends to her baby when he cries and cuddles him until he is quiet, she may teach him that if he cries he will get attention from mother. Thus, the baby will learn to increase his crying in order to have his mother more.
Every day, we grow and have new experiences. We constantly learn by reading, watching television, interacting with other people, and so forth. This learning affects our emotions. Why is it that we learn to like some people and dislike others？ If a person is nice to us, cares about us, we learn to associate this person with positive feelings, such as joy, happiness, and friendliness. On the other hand, if a person is mean to us, does not care about us, and even deliberately does things to harm us, we learn to associate this person with negative feelings, such as unhappiness, discomfort, and anger.
What's the author's main purpose in writing the passage？

A. To teach children how to learn to produce and experience certain emotions.
B. To give the general reader an account of two basic kinds of learning.
C. To give parents some advice on how to modify their children's emotions through earning.
D. To discuss with psychologists how positive and negative feelings are produced.