The grapes are now ...... enough to be picked.

Answer: Option C

The grapes are now ripe enough to be picked.
In this context, "ripe" specifically refers to fruits being fully developed and ready to be harvested, making it the most suitable choice among the options provided. When grapes reach this stage of ripeness, they have attained the optimal balance of flavor, sweetness, and juiciness, making them ideal for consumption or processing into various products such as wine. Therefore, "ripe" accurately describes the readiness of the grapes for harvesting.