Answer:
(D) both experience events that test their self-assurance
Step-by-step explanation:
In different excerpts from A Club Pilot and No gumption the narrator have experiences in events that test their self assurance, for example in a A Club Pilot often remembers events form his past while having doubtful thoughts, so the thing that Twain´s and Baker´s novels is the fact that (D) both experience events that test their self-assurance.