To find the expected number of deer in an area of 300 square miles, we can first calculate the deer density in the area sampled.
The scientist found 200 deer in 10 square miles, so the deer density is:
\[ \text{Density} = \frac{\text{Number of deer}}{\text{Area}} = \frac{200 \text{ deer}}{10 \text{ square miles}} = 20 \text{ deer per square mile} \]
Now, to find the expected number of deer in 300 square miles, we can multiply the density by the new area:
\[ \text{Expected number of deer} = \text{Density} \times \text{Area} = 20 \text{ deer per square mile} \times 300 \text{ square miles} = 6000 \text{ deer} \]
Therefore, the scientist can expect to find 6,000 deer in an area of 300 square miles.
The correct response is: 6,000 deer.