To determine the percentage of farmers with sandy soil who prefer producing carrots, we need to calculate the relative frequency of farmers who prefer carrots among those with sandy soil.
The number of farmers with sandy soil who prefer carrots is 120. The total number of farmers with sandy soil is 170.
We can find the percentage by using the formula:
\[ \text{Percentage} = \left( \frac{\text{Number of farmers preferring carrots}}{\text{Total number of farmers with sandy soil}} \right) \times 100 \]
Substituting in the numbers:
\[ \text{Percentage} = \left( \frac{120}{170} \right) \times 100 \approx 70.588% \]
Rounding this to the nearest tenth gives:
\[ 70.6% \]
So, the correct answer is 70.6%.