Choose the term that best describes the underlined part of the sentence. Tony realize that Maria was not going to show up. A independent clause B adjective clause C adverb clause D noun clause

The correct answer is D. noun clause.

The clause Maria was not going to show up cannot be independent because it depends on the first part of the sentence. What did Tony realize? - That Maria was not going to show up.

Since it doesn't describe a noun or a verb, it cannot be an adjective/adverb clause either.