The fastest way through this paragraph is to track three phrases that only make sense once something earlier has named them: "this aspect" in one sentence, "despite the awareness" in another, and "these defaulters" in a third.
"This aspect of our economy" in the awareness sentence must be pointing back to a sentence that has already named a specific part of the economy, which only the income tax sentence does. So the income tax sentence has to come first, and the awareness sentence right after it. "Despite the awareness" then needs that awareness sentence to already exist, so the sentence about citizens failing to pay tax has to come after it, not before. Finally, "these defaulters" needs the citizens who fail to pay tax to have already been introduced, so the sentence about defaulters creating extra work has to be last.
Chaining these dependencies together gives income tax first, awareness second, citizens who ignore it third, and the trouble they cause last.
So, the correct answer is bcad.
Another approach is to follow only the connecting words and pronouns across the four sentences, setting the overall meaning aside for a moment.
Tracing just the words "this aspect," "despite the awareness," and "these defaulters" back to their sources lands on the same sequence.
So, the correct answer is bcad.