The correct answer is: can solve.
The verb “solve” is a transitive verb, which means it takes a direct object. In this case, the direct object is “this puzzle.” The verb “can” is a modal verb, which means it expresses ability or possibility. In this case, the modal verb “can” is used to express the speaker’s ability to solve the puzzle.
The other options are incorrect because they do not make sense in the context of the sentence. Option A, “can, solved,” is incorrect because the verb “solved” is in the past participle form, which is used to form the perfect tenses. In this case, the speaker is not talking about the past, so the past participle form is not appropriate. Option B, “can be, solved,” is incorrect because the verb “be” is a linking verb, which means it does not take a direct object. In this case, the speaker is talking about the speaker’s ability to solve the puzzle, so the linking verb “be” is not appropriate. Option C, “do, solved,” is incorrect because the verb “do” is an auxiliary verb, which means it does not take a direct object. In this case, the speaker is talking about the speaker’s ability to solve the puzzle, so the auxiliary verb “do” is not appropriate.