Shelly has a green and . . . . . . . . black trousers. A. a B. an C. the D. no article

The correct answer is D. no article.

The word “trousers” is a plural noun, so it does not need an article. The word “a” is used before singular nouns that refer to a general or unspecified thing. The word “an” is used before singular nouns that begin with a vowel sound. The word “the” is used before singular nouns that refer to a specific thing.

In this case, Shelly has a pair of trousers, so we do not need to use an article. We could also say “Shelly has green and black trousers.”