From the words or groups of words lettered A to D, chose the word or group of words that best completes the sentence. This...be David's handwriting: I know ...

Answer Details

The best option to complete the sentence is "can't". The speaker is confident that the handwriting cannot be David's, indicating that they are familiar with his handwriting and are sure that the handwriting in question is not his. "May" implies possibility, "will" implies certainty about the future, and "ought" implies obligation, none of which fit the context of the sentence.