Step 1: Analyze the sentence for subject-verb agreement.
The subject of the sentence "the number of people" is singular, so the verb should be "is," not "are." Additionally, the comparison should be made using "the number of people who died due to."
Step 2: Analysis of options.
- (A) are less than: Incorrect. The subject is singular, so the verb should be "is," not "are."
- (B) are fewer than: Incorrect for the same reason as option (A).
- (C) is less than those who died due to: "Those" is incorrect because it doesn't properly refer to "the number of people."
- (D) is less than the number of people who died due to: Correct. This option correctly uses "is" and provides a proper comparison.
- (E) is less than that of people who died due to: "That of" is awkward and not as grammatically correct as "the number of people."
Step 3: Conclusion.
The correct answer is (D), as it matches both subject-verb agreement and makes the comparison logically clear.