Toni has . . . . . . . . terrible Stomach ache. A. a B. an C. the D. no article

The correct answer is D. no article.

The article “a” or “an” is used before singular nouns that refer to a general or indefinite thing. In this case, the noun “stomach ache” is singular and refers to a specific stomach ache that Toni is experiencing. Therefore, we do not use an article.

The article “the” is used before singular nouns that refer to a specific or unique thing. In this case, the noun “stomach ache” is singular, but it does not refer to a specific or unique stomach ache. Therefore, we do not use the article “the.”