The correct answer is: Yes, because the trees in the sample are chosen randomly. The sample size also appears to be large enough to avoid bias.
The farmer's generalization is valid because she randomly selected a sample of trees, which helps to ensure that the sample is representative of the overall population. Additionally, the sample size of 700 trees is sufficiently large to avoid bias in the results, assuming the trees are homogeneously distributed and similar in terms of apple sweetness.