Решение:
Нужно вставить сравнительную степень прилагательных:
- People in the countryside are friendlier (friendly) than they are in the city.
- These suitcases were heavy, but this one was the heaviest (heavy) of all.
- Mary is as pretty (pretty) as Nancy.
- Ann was the most beautiful (beautiful) girl I knew.
Ответ: 1. friendlier, 2. heaviest, 3. pretty, 4. most beautiful.