11) Empty is describing cabin and small is describing meadow.
12) Rapid is describing river and muddy is describing the banks.
13) Hungry and weary both describe the hikers.
14) Ancient is describing the bridge and deep is describing the water.
15) Remote and lonely are both describing the place.
16) Correct is describing the path, and it is also described as not being clear.
17) Smart and practical describe the hiker, and warm describes the fire.
18) The person is described as 'other' and the map is described as large.
19) Small is describing the compass and extra describes the food.
20) Fresh describes the water and clear describes their course home.
These are all the adjectives in the paragraph in exercise C: New, last, unlucky, easy, smooth, barely (barely is an adverb but I'm assuming it counts in this exercise because it says one sentence has more than one adjective and none of the other sentences have anything else.).
a point of view and a viewpoint are essentially the same thing. They both refer to an attitude or a way of thinking about a particular subject, e.g. Try looking at things from a different point of view. Try looking at things from a different viewpoint.
It's because the 'chicken and dumplings' is renaming the noun 'meal' that is already there. Usually to find an appositive phrase, just look beside the noun and see if the sentence works without the words beside it.