Which sentence is most clearly written?

The first sentence is more clearly written because it emphasizes the action and the comparison in a straightforward manner. It presents a clear cause-and-effect relationship by stating that in rural areas, a higher number of deer fatalities result from automobiles compared to hunters. This phrasing provides a clear numerical comparison without ambiguity regarding the subjects involved.

Moreover, the use of "killed by" maintains a passive construction that clearly indicates the agent responsible for the action—in this case, automobiles. This slightly more formal structure helps to ensure that the reader understands the context of the sentence fully. By explicitly stating that more deer are killed by automobiles, it underscores the significant impact of traffic on wildlife.

In contrast, the second sentence, while also clear, uses "automobiles kill more deer," which could imply a more active voice yet may introduce a sense of immediacy that could mislead the reader into thinking about direct encounters rather than the broader context of annual deer fatalities. It is less formal and could be interpreted as suggesting a causal relationship that is less thoroughly examined.