The answer is correct because testing the hypothesis that a RAM module is defective entails removing the suspected bad module and replacing it with a known good one. If the errors and instability cease, this suggests that the original RAM was likely the cause of the problem. On the other hand, if the system remains unstable, the issue may lie elsewhere, and a new theory must be established. It's crucial to methodically follow troubleshooting steps to avoid unnecessary replacements or repairs.