If something is ambiguous, the pronoun is not specific. For example, number one is correct. "They were smiling, pleased, and happy." This could refer to either the people in the audience or the rock band. Does this make sense?
1. Ambiguous "The rock band waved to the smiling, pleased, and happy people in the audience."
2. Unambiguous
3. Unambiguous -- simply due to syntax
4. Ambiguous "Some British and French students took part in a foreign exchange, but unfortunately both ethnicities disliked the food."
5. Unambiguous -- although "with her" should be a bit more specific.
