To answer this question, the user needs to have basic knowledge of database architecture and file systems.

The biggest advantage of having control files on different disks is to guard against failure. Option B is the correct answer.

Explanation for each option:

A. Database performance: Although disk performance can impact database performance, having control files on different disks does not necessarily improve database performance.

B. Guards against failure: When control files are located on separate disks, it provides redundancy and a safeguard against disk failure. If one disk fails, the other disk can still provide the necessary control files for the database.

C. Faster archiving: Control files are not directly related to archiving. Having control files on different disks does not necessarily speed up archiving.

D. Writes are concurrent, so having control files on different disks speeds up control file writes: While it is true that having control files on different disks can speed up control file writes, this is not the biggest advantage of having control files on different disks. The biggest advantage is the redundancy and safeguard against disk failure.

Therefore, the correct answer is:

The Answer is: B. Guards against failure.