Those Questions!

a) I believe plot is necessary, although I believe it would be possible to write a work of fiction without". Including your own defintion of plot, consider the relative importance and impact of plot on works in your study in the light of the above quotation.
This question is asking you to define the term plot in your own words and discuss how the plot's existance is significant, or insignificant, in writing a work of literature.
Obviously, plot would have to be the element talked about the most in this essay.

I would choose to use Darkness at Noon and As I Lay Dying.

b) Symbols and motifs are an essential element of many novels or short stories. How have either or both of these devices been used and, in your opinion, how successfully, in two or three works you have studied?
This question is asking you to examine the importance and the role of these literary devices within literature and wants to know how this can be applied to the works in which we have studied.
The primary literary techniques I would use would be the motifs and symbols.
I would use The Bluest Eye and Metamorphosis.