There are four types of sentence functions: interrogative, imperative, exclamatory, and declarative.
Interrogative sentences are questions. Exclamatory sentences are exclamations, or sentences that end in exclamation points. Imperative sentences are orders, or commands, like "Eat your lunch." Declarative sentences are statements that end in a period, like "Today is my ballet practice."
"Question" is not a sentence function--instead, questions are called interrogative--so the correct answer is D.
Answer: D