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Answer:
a, b, c --- all not representative
Explanation:
The question posed by the engineer is "are residents of the city in favor of ...".
The only representative sample is one from a pool that includes all residents of the city—not just those who (a) use the road, (b) live along the road, or (c) own homes.
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Additional comment
The engineer may want to refine the question. As posed, it would include children, homeless, and/or institutionalized residents of the city as well as drivers and tax-payers. In inclusive cultural traditions, "residents of the city" may also include animals, plants, water, air, and other holders of spiritual energy.