Question: who plays sir gregor in the game of thrones
[{'answer': 'Hafþór Júlíus Björnsson', 'provenance': [{'wikipedia_id': '1316115', 'title': 'Gregor Clegane', 'start_paragraph_id': 3, 'start_character': 190, 'end_paragraph_id': 3, 'end_character': 213, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]