Final answer:
The sentence indicating that an online group uses gaming to practice Korean together best supports the effectiveness of video games in practicing skills learned in the classroom.
Step-by-step explanation:
The sentence from the article that BEST supports the statement that video games can be an effective tool for helping students practice skills that may feel irrelevant in a classroom is D. His online group Korean Language Exchange has 690 members who game or just practice Korean together. This example directly illustrates how gaming can facilitate the practice of language skills outside a conventional classroom setting, embodying the concept of learning through play. It suggests that video games can not only engage students in a fun activity but also offer a platform for practicing real-world skills, like language acquisition, in a collaborative and interactive environment.