Complete the sentences using the correct superlative forms.

1. Olga is the smartest in the class. 2. That mountain is the highest in the region. 3. This car is the fastest of all. 4. He is the richest person in the city. 5. This problem is the most difficult we've encountered. 6. That was the funniest joke I've heard. 7. This is the most dangerous sport in the world.