Agreed. At this point people have been conditioned to expect the back button to lose their place or take them off the domain. So it's important to have a way in the webapp's UI even if you have the back button behaving properly.
Wonder how age factors into it. Poor Americans are probably more likely to marry in the early 20s, vs career-minded professionals in large metros who wait till their 30s.
I wouldn't take much away from a multiple choice question about such big, abstract, interconnected concepts.