by Sage Pearce-Higgins Mon Oct 22, 2018 5:32 pm
I think that's a pretty good trap for this problem. Yes, we'd look for some stronger connection between the two facts (after all, we can see that the intended meaning is that by leaving their cars open, some people encourage bears). However, the idiom issue trumps all, meaning that all answers except D and E can be eliminated.
As much as we might want to say "who fail to lock their cars at night and who therefore expose their cars and other campers to" to make sure that we're talking about the same people, we don't have to. So long as the meaning is clear, we can make use a parallel construction to refer to the same people. The meaning of the sentence shows us that the two events (leaving your car open and encouraging bears) are clearly connected.
In fact, since the sentence only talks about one group of people, it's pretty logical to assume they are the same people. A sentence such as this one would be much more problematic: 'Police have started to fine people who cycle on the pavement and who drive cars without headlights.' That makes it sound like the same people are doing both. Clearer would be to say 'Police have started to fine people who cycle on the pavement and people who drive cars without headlights.'
A good problem: it made you doubt the correct answer by not providing what you expected, and perhaps encouraged you to choose something totally wrong, such as 'expose ... their cars ... with bears'