The subordinate clause here is A, "as the layers of ash slowly compressed". Subordinate means that it cannot exist on its own, it has to be a part of the main, independent clause.
Answer:
I think in the first column you have to put "children who bring lunches.." and "the national.. "( the one that has citations). The rest goes to the other column
Expanation:
I think that it would be Unplugging the computer, because you are either
a. you are doing something that would effect the computer
or
b. because you are being more active
??
to enable the character to share thoughts with the reader directly
"in the desert" and "begun to desert" are both spelt identically but have different meanings- so D. heteronyms