Final answer:
The phrase 'I couldn't agree with you more' means that the speaker totally agrees with the other person's statement to the fullest extent possible. The correct answer to the question is A. totally agree.
Step-by-step explanation:
When someone says, "I couldn't agree with you more," it is an emphatic way of expressing complete agreement with someone's opinion or statement. It means that the person fully shares the viewpoint or sentiment being expressed and there is no room for more agreement; it is the maximum level of concurrence. This phrase is typically used in conversational English to acknowledge that one holds the exact same position or feelings as the other person without any reservations.
The correct answer to the question "If you say, 'I couldn't agree with you more,' what does it mean?" is A. totally agree. The statement does not imply any kind of disagreement or uncertainty. Therefore, options B, C, and D do not correspond to the meaning of the phrase.