To answer this question, you need to understand the purpose of the different UNIX commands related to writing data to disk.
Option A) write - This option is incorrect because the "write" command is used to send messages to other users or terminals, not to write data to the disk.
Option B) sync - This option is correct because the "sync" command is used to flush file system buffers and write in-core super block and inode table information to the disk. It ensures that all pending disk writes are completed and that the file system is synchronized.
Option C) insync - This option is incorrect because there is no "insync" command in UNIX. It is not a valid command.
Option D) write_core - This option is incorrect because there is no "write_core" command in UNIX. It is not a valid command.
The correct answer is B) sync. This option is correct because the "sync" command is used to write in-core super block and inode table information to the disk, ensuring that all pending disk writes are completed and that the file system is synchronized.