The answer is a. The general idea of the essay should come first.
D. That all aspects of the piece should work together to create a certain effect
To create a "unity of effect" on the reader, it should have a certain effect on the reader. Like a really sad and depressing book should not exactly make the reader sad, but to feel the parts of the book that spoke out to the reader.
If the root hydro- means "water", then the word that means "an electrical instrument used to monitor underwater sounds" is called a hydrophone. A hydrophone is a kind of microphone that is specifically used to detect and record sound waves underwater.
That literary movement is known as modernism.
Modernism came to be after WWI, as a response to both the war and the previous literary eras. It wanted to change everything we knew about literature, which is why it used many experimental techniques to wow the audience and make them think.