Select the most appropriate ANTONYM of the underlined word in the following sentence.
You should never visit her without her consent.

The correct answer is Refusal.

Understanding the underlined word:
The word "consent" means giving permission, agreement, or assent for something to happen. In the context of the sentence, "without her consent" means without her permission or agreement.

Analyzing the options:
1. Permission: This means official allowance or consent. This is a synonym of "consent".
2. Knowledge: This means information, understanding, or awareness gained through experience or education. It is not an antonym of "consent".
3. Approval: This means the action of approving something or agreeing to it. This is a synonym of "consent".
4. Refusal: This means an act of showing or expressing unwillingness to do, give, or accept something. This is the exact opposite (antonym) of giving consent or permission.

Therefore, the most appropriate antonym of the word "consent" is Refusal.