_unit_id  : unique work unit id
_created_at : task completion timestamp
_golden : TRUE if a gold question
_id : unique item id
_missed : TRUE if this is an incorrectly answered gold question
_started_at : task start timestamp
_tainted : see crowdflower docs
_trust : see crowdflower docs
_worker_id : unique worker id
please_decide_which_passage_is_more_difficult : the worker response.  if they thought passage A was more difficult than B, this field is set to "Passage A is more difficult." and respectively for passage B.  May also be "I don't know or can't decide".
label_level_a : the true grade level (American grade 1-12) for passage A
label_level_b : the true grade level (American grade 1-12) for passage B
passage_a : the 50-word text passage A
passage_b: the 50-word text passage B
please_decide_which_passage_is_more_difficult_gold : the correct gold response, e.g. "Passage A is more difficult." if passage A has higher grade level than passage B.