Answer :

The word that would most likely introduce a counterclaim is "however."

Here's why:
1. "However" is often used to introduce contrasting or opposing ideas in a sentence. When presenting a counterclaim, you are providing an argument that goes against the main claim or thesis statement.
2. A counterclaim is a statement that challenges or opposes the main argument or claim being made. It offers an alternative perspective or viewpoint.
3. By using "however" to introduce a counterclaim, you signal to the reader that you are about to present a different viewpoint that contradicts the initial argument.

In summary, when you see the word "however" in a sentence, it's a strong indicator that a counterclaim is being introduced to challenge the main idea presented.