Select the most appropriate synonym of the given word.
Confidential

The correct answer is Secret.

Explanation:

The word "Confidential" refers to information that is intended to be kept secret or private, not to be disclosed to unauthorized persons.

Let's analyze the given options:

1. Limited: Restricted in size, amount, or extent; not an exact synonym of confidential.
2. Secret: Kept private or hidden from others, which directly matches the meaning of confidential.
3. Open source: Denoting software or information whose source code or details are made freely available to the public.
4. Public: Open to or shared by all people; this is an antonym of confidential.

Therefore, the most appropriate synonym for Confidential is Secret.