The correct option is D Walk
Come is the base form of the verb, its past form is came and its past participle form is come. Come is an irregular verb as its past and its past participle is not formed with the addition of -ed at the end base form of the verb. Therefore, options A 'come' and 'came' are incorrect, whereas, coming is the continuous form of the verb come, therefore, option C is incorrect. The correct option is option D, as 'walk' as its past and past participle form is 'walked'. It's a regular verb because we've simply added an -ed to form the past and past participle form of the base verb 'walk'.