Medics have a tough job of trying to heal the wounded because they are normally hurt in dangerous scenarios.

Who is "they" in this prior sentence?
the wounded
The peace emissaries arrived to negotiate a peace treaty for the warring population, but they will be difficult to find common ground for.

Who is "they" in this prior sentence?
the warring population
Some people proclaimed at the Ontario conventions that we need to colonize planets in the near future since they are places where people can voice these kinds of concerns among like minded people.

Who is "they" in this prior sentence?

the Ontario conventions