Question: what does the b in hb pencil stand for
[{'answer': 'black', 'provenance': [{'wikipedia_id': '24508', 'title': 'Pencil', 'start_paragraph_id': 3, 'start_character': 145, 'end_paragraph_id': 3, 'end_character': 150, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '24508', 'title': 'Pencil', 'start_paragraph_id': 76, 'start_character': 0, 'end_paragraph_id': 76, 'end_character': 959, 'bleu_score': 0.9874601949752461, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 8600809255002808383}, 'section': 'Section::::Grading and classification.\n'}]}]