question_subject:
Science
question_exam:
CDS-II
stats:
0,18,35,5,9,38,1
keywords:
{'gases': [0, 0, 5, 12], 'landfills': [0, 0, 0, 2], 'methane': [0, 0, 0, 5], 'nitrogen': [1, 1, 0, 2], 'oxygen': [3, 0, 1, 0], 'hydrogen': [0, 0, 1, 3], 'urban areas': [0, 0, 0, 1]}