He was always prepared to refute the idea.

The correct answer is A. agree.

To refute means to argue against something, to express disagreement with it. The other options do not mean the same thing.

• To subscribe means to agree to receive something, such as a magazine or a newsletter.
• To recommend means to suggest that someone do something, or to say that something is good.
• To endorse means to give support or approval to something.

In the sentence “He was always prepared to refute the idea,” the speaker is saying that the person was always ready to argue against the idea. This means that the person did not agree with the idea, and was prepared to give reasons why they did not agree.