A、People tend to go to extremes in daily life. B、People try all out to build a perfect relationship. C、People change themselves

Are you looking for a good relationship with someone special? What type of person is the best person for you? Is it the person with the highest IQ? Is it the most beautiful or most handsome person? How about the richest person or the most ambitious? Is your ideal partner the most traditional or the most modern person? Is he or she the person like you, or most unlike you?
    The answer, psychologists say, is none of the above. Why? Because they are all extremes. In a number of research studies, psychologists asked couples these questions. The answers were clear. Most people are happy with moderation—with partners who are not the most or the best, or the least or the worst. People are more comfortable with partners who are not so special.
    The research showed several other important things. In a love relationship, two things can cause trouble. First, trouble happens when both people get angry quickly. This is not surprising. Second, trouble happens when people don’t expect to change themselves in a relationship. Do you stay calm when you disagree with someone? Are you ready to change yourself? If you can tolerate disagreement and are willing to change, maybe you are ready for a serious relationship.
16. What’s the passage mainly about?
17. What’s the result of the research studies?
18. According to the speaker, what are essential for a serious love relationship?