Solution:
- It's the nationality of a person from Switzerland.
- It's the country where Argentinian people live.
- It's the man whose father is your grandfather.
- It's the crime that thieves commit.
- It's the person who copies DVDs and software illegally.
- It's the period when you are a child.
- It's a country where people speak Portuguese.
- It's a thing that you often do after school.
Answer: 1. (omitted), 2. where, 3. whose, 4. that, 5. who, 6. when, 7. where, 8. that.