Is this a multiple choice question?
The first box is a dangling modifier. The second is a clause. The last is a phrase. (Answers going from top to bottom) :)
Answer: The couplet allows for parallel form connecting the elements of thought.
Here are the connections:
God directs - from his head
guard him from on high- let ev'ry evil fly
Water!
Photosynthesis produces sugar and oxygen, and doesn't require or produce carbon, thus it must be water.