Choose the correct word

1. The natives have lived
   [ on|at] the continent for many years.
2. Please send the letter
   [by|at] air mail.
3. Admission to the ceremony is
   [by|in] invitation only.
4. The celebration is held
   [on|at] holy ground.
5. The Australian Aboriginals are famous
   [at|for] their handmade art.
6. The politician asked his supporters to come together
   [in|on] unity.