フリー問題

問題文

Why can output written through a buffered writer fail to appear on disk?

選択肢

1. The characters unconditionally stay inside the intermediate array until the program performs one explicit reading step or one close.
2. The characters unconditionally stay inside the intermediate array until the program performs one explicit flushing request or one close.
3. The characters unconditionally stay inside the kernel queue until the program performs one explicit reading step or one close.
4. The characters unconditionally stay inside the kernel queue until the program performs one explicit flushing request or one close.