How frequently has Ben traveled overseas for language learning?

The statement "Often enough" indicates that Ben has traveled overseas for language learning with a frequency that is considered adequate or beneficial for his language acquisition. This implies that he has sufficient opportunities to immerse himself in a foreign language environment, which is crucial for improving language skills. Traveling overseas exposes Ben to native speakers, cultural contexts, and real-life practice, all of which enhance his learning experience.

The other options suggest varying degrees of infrequency or insufficiency in travel frequency for language learning, which do not align with the idea of having made adequate use of opportunities to learn. Therefore, "Often enough" conveys the most favorable situation regarding Ben's overseas experiences in language learning.