Respuesta :
First, define interrogative. Interrogative means having or conveying the force of a question. There is only one question in the answer choices, so it has to be: "Do you know the answer?"
The correct answer is " Do you know the answer?". In grammar, the interrogative mood is defined as the verb category at which the verb expresses a question. In this case the verb "do" expresses the question if the other persons knows the answer, which can be easily spotted by the question mark.