Question: who played the master on buffy the vampire slayer
[{'answer': 'Mark Metcalf', 'provenance': [{'wikipedia_id': '625884', 'title': 'Master (Buffy the Vampire Slayer)', 'start_paragraph_id': 1, 'start_character': 166, 'end_paragraph_id': 1, 'end_character': 178, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '625884', 'title': 'Master (Buffy the Vampire Slayer)', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 795, 'bleu_score': 0.960470563889473, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 2636693396026716406}, 'section': 'Section::::Abstract.'}]}]