I would have to say D, I think you forgot the commas, but it is the only one that does not, or could not have commas.
It's subordinate. Meaning that it is dependent on the main clause.
The answers are: <em>a. exposition, b. climax and d. falling action.</em>
Exposition, climax and falling action are part of the basic plot structure. Plot is a sequence of events, it refers to a conflict, and it's also the main part of a story.
Exposition: the beginning of the story and introduction of the conflict.
Climax: it's the turning point of the story.
Falling action: when events begin to resolve and the story works toward its end.
Circumstances that may cause you to lose sleep is the mental health issue: Insomnia; You could be a physically healthy person but mentally not so much and it can seriously cut back on the amount of sleep you get. Factors that can cause you to lose sleep are: An uncomfortable bed, stress and anxiety, overthinking, not enough production throughout the day, light and sound.
Hope this helped :)