PREPOSITIONS OF PLACE: AT, IN, ON or TO

I met him by chance ___ the bus stop the other day.
1. at
2. in
3. on
There are too many people ___ that boat. It´s going to sink.
1. on
2. in
3. at
It´s late. I must go ___ home.
1. to
2. -
3. at
They met ___ university. That was quite a long time ago.
1. at
2. in
3. to
She´s just had an operation, so she has to remain ___ hospital for another week.
1. in
2. at
3. on
I´m looking forward to going to Australia, although I´ll be there ___ business.
1. in
2. on
3. to
I don´t feel like going out. I think I´ll stay ___.
1. in
2. at
3. on
They live ___ the fourth floor.
1. in
2. on
3. at