Japanese IQ Test

Apparently this is an IQ test given to job applicants in Japan.

"Everybody has to cross the river"

The solution:

1. Cop/Thief go, Cop comes back
2. Cop/Son go, Cop/Thief come back
3. Father/Son go, Father comes back
4. Mother/Father go, Mother comes back
5. Cop/Thief go, Father comes back
6. Mother/Father go, Mother comes back
7. Mother/Daughter go, Cop/Thief come back
8. Cop/Daughter go, Cop comes back
9. Cop/Thief go