Answer:
B. Declarative Sentence
Step-by-step explanation:
A declarative sentence is a type of sentence that makes a statement or expresses a fact. In this case, the sentence "I don't know the answer" is a declarative sentence because it is simply stating a fact or making a statement about the speaker's lack of knowledge regarding the answer to a question. Declarative sentences are the most common type of sentence in the English language and are used to convey information, provide explanations, or express opinions. They typically end with a period (.), and the main purpose is to convey information or make a statement rather than ask a question, give a command, or express strong emotion.