question:  What best describes the overall structure of Captain Hannah's dialogue when recounting his time caring for the marocca plants?
context: Captain Hannah climbed painfully down from the Delta Crucis , hobbled across the spaceport to where Beulah and I were waiting to greet him and hit me in the eye. I only drink rhial when I've been exposed to Captain Hannah. But when I offered them a sizable piece of cash plus a perpetual share of the profits for letting us take a load of marocca plants to Gloryanna III, they relented and, for the first time in history, gave their assent. "When I left, marocca was growing like mad," said Captain Hannah. "You'll remember that I warned you that we should take some marocca out into space and solve any problems we might find before committing ourselves to hauling a full load of it?" asked Captain Hannah. If we had gone through all of that rigamarole, we would have lost the franchise. I almost asked him why he had been barricaded in the bathroom of the Delta Crucis , but I figured it was safer to let him tell me in his own way, in his own time. So I lined up the Delta Crucis perpendicular to her direction of motion, put a once-every-twenty-one hour spin on her to match the rotation rates of Mypore II and Gloryanna III, and uncovered the view ports to let in the light. It gradually brightened until 'noon time', with the ports pointing straight at the light source, and then dimmed until we had ten and one-half hours of darkness. "Oh," said Captain Hannah in quiet tones of controlled desperation, "it was very simple. "Of course, first I had to move all the hydroponic tanks from their original positions perpendicular to the axial thrust line of the ship to a radial position. And because somehow we had picked up half of the plants in the northern hemisphere of Mypore and the other half in the southern hemisphere, it turned out that half of the plants had a sinistral corkscrew and the other half had a dextral.
output:  A problem-solution structure.
options:  An argument and supporting details along with counterclaims structure.  A catchphrase followed by explanations structure.  A purpose and explanation structure.  A problem-solution structure.