Many many small bubbles
There seem to be many small bubbles in the emission nebula, too numerous and too difficult to mark because it is very hard to circularize the tool and place it; I marked but a few of the larger ones. Or do I miss the point? I think the tutorial is too vague and should clarify the categories better.
Hey eugenius, have you looked at the "Guide" section? There are more examples of each object type.