Question: who played clark griswold son in christmas vacation
[{'answer': 'Johnny Galecki', 'provenance': [{'wikipedia_id': '1125221', 'title': "National Lampoon's Christmas Vacation", 'start_paragraph_id': 1, 'start_character': 378, 'end_paragraph_id': 1, 'end_character': 392, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '1125221', 'title': "National Lampoon's Christmas Vacation", 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 448, 'bleu_score': 0.9716239638199891, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3838547274105145089}, 'section': 'Section::::Abstract.'}]}]