How do I unload a scene after doing LoadLevelAdditive?

I have scene A loaded.

I load scene B with LoadLevelAdditive.

How do I unload scene B and keep scene A loaded?

Found the answer. When scene B is loaded, the objects are just thrown in without any marking about what scene they came from. So I need a way of knowing which objects came from scene B, and I have to Destroy() them all manually.

One way is for every object in scene B to be under one parent object. Calling Destroy() on that parent object will remove the whole of scene B.