English plurals

No language can thrive without having a way for its speakers to express things in the plural; for example, two desserts are always better than one. As you know, most English nouns form their plurals by adding s or es. But a simple rule with no exceptions would be boring, don't you think? Test your knowledge by choosing the correct plurals for the words below.

1. The plural of potato is Placeholder for the answer.
2. The plural of fraternity is Placeholder for the answer.
3. The standard plural of caribou is Placeholder for the answer.
4. The recommended plural of phenomenon is Placeholder for the answer.
5. The standard plural of surplus is Placeholder for the answer.
6. The plural of kibbutz is Placeholder for the answer.
7. The standard plural of brother-in-law is Placeholder for the answer.