The author concludes that the residents of Sierra should vote in favor of a local tax to fund construction of the proposed road.

Why?

Because in order for the Glen Veil apartment complex to be built, a road connecting it to the town of Sierra must be built.

The apartment complex, if completed, would strenthen Sierra’s economy, which would benefit every Sierra resident.

The conclusion asserts that the residents of Sierra “should vote” for something. But the premises don’t tell us when the residents “should vote” for something. We want a principle that gets us from the premises to the conclusion that the residents “should vote” for a local tax for the proposed road.

What are the features of the proposed road, as described by the premises? We want to connect those features to why the residents should vote for the local tax.

The proposed road is described necessary for the apartment complex, which is something that would benefit every Sierra resident.

Here’s an example of a principle that would strengthen the argument:

If something is necessary for another thing, and that other thing would help every resident of a town, then the residents of that town should vote for a local tax to fund the necessary thing.

Let’s keep an open mind, since the correct answer doesn’t have to look exactly like that example principle.