The correct choice is Option 2: 'Because he wanted to become better at conversing in Japanese.' The text states: '日本語をもっと上手に話せるようになりたいと思ったからです' (It was because he wanted to become able to speak Japanese more fluently). Although suggested by a friend, Option 1 is incorrect because the friend only recommended it, not forced him. Options 3 and 4 are not mentioned.