Option 1: Argue that Jodahs either represents the successful solution of the "human contradiction," or the failure to solve it. If you wish, you might relate Jodahs success/failure (either as an individual or an experiment) to the Akjai - for instance, to the success/failure of either the human or the Oankali Akjai.
Option 2: Again, using a small set of passages from Imago, discuss how we can use the title of the third novel to analyze its contents. In other words, base an argument about some part of the novel on what the word imago means - defend your arguments in detail, avoiding speculation!
Option 3: Explore in detail, through the use of passages from Imago and either Adulthood Rites or Dawn, the purpose or the impact of having the third novel written in first person, whereas the first two were written in the third person. Think of this as a way of relating the form of the trilogy to its content - what does it mean that we make the transition between first and third person when and how we do.