Since we should not disclose our identity, our letter to the principal must be …

Analyze the question The sentence says we should not disclose our identity. So we need a word that describes a letter whose writer's name is not revealed.

Explain the concept This is a vocabulary-in-context question. The clue is "not disclose our identity", and you match it to the word with that meaning.

Check each option

• A. unclear: means not easy to understand. It is about the message, not about who wrote it. ✗
• B. anonymous: means written or done by someone whose name is not known or not given. ✓
• C. ambigous (correct spelling: ambiguous): means having more than one possible meaning. This has nothing to do with identity. ✗
• D. candid: means frank and honest. A candid letter can still carry the writer's name. ✗

Solution "Since we should not disclose our identity, our letter to the principal must be anonymous."

Tip Look for the clue phrase in the sentence ("not disclose our identity"). Then link it to the word's root: anonymous comes from Greek an- (without) + onoma (name), so it literally means "without a name". Also note that "ambiguous" is spelled with a u, so remember it as ambi-gu-ous.