Ответ:
1. Ryan plays in the most successful basketball team in the country.
2. Emma is so kind. She's the least selfish girl in our class.
3. Are you less pessimistic now than you were last year?
4. I don't talk much. I'm the quietest person in our group.
5. In our music lessons Karl sings more loudly than Ben.
6. Why did you come last in the race? Because I ran most slowly!