A group of lions is called a pride. A group of fish swim in a shoal. Teacher (choice a) and student (choice b) refer to another meaning of the word school. The answer is not (choice c) because self-respect has no obvious relationship to this particular meaning of school.
An optimist is a person whose outlook is cheerful. A pessimist is a person whose outlook is gloomy. The answer is not (choice b) because a pessimist does not have to be mean. (Choices c) and d are incorrect because neither adjective describes the outlook of a pessimist.