Of course . . . . . . . . beaver was startled. It slapped its tail and disappeared into the pond. A. a B. an C. the D. no article

The correct answer is D. no article.

The sentence is about a specific beaver, so we do not need to use an article. The beaver is not just any beaver, it is the beaver that was startled.

If we were to use an article, it would change the meaning of the sentence. For example, if we used “a” beaver, it would mean that any beaver could have been startled. But the sentence is about a specific beaver, so we do not need to use an article.

The other options are incorrect because they are all articles. An article is a word that is used to introduce a noun. In this case, the noun is “beaver.” We do not need to use an article because the sentence is about a specific beaver.