Choose the correct answer. Sorry, I ... (not know) the answer.

The correct answer is "don't know". The complete sentence is: "Sorry, I don't know the answer." **Explanation:** The sentence expresses a lack of knowledge. The phrase "not know" needs to be conjugated correctly to fit the sentence's grammar. * "not know" is grammatically incorrect. * "do know" implies knowledge, which contradicts the meaning of "sorry". * "am not knowing" is a continuous tense, which is not appropriate here. We usually use simple present in that situations. * "don't know" is the correct contraction of "do not know", expressing a lack of knowledge in simple present tense, fitting the context perfectly. Thus, the correct answer is: don't know