questions
subject_id
question_no
source
source_year
question_type
question_subtype
stem
stem_plain
answer
analysis
hint
difficulty
estimated_time
score
primary_kp_id
knowledge_tags
version
parent_question_id
is_template
status
is_active
quality_score
usage_count
correct_rate
avg_time_spent
tags
JSON 格式
extra_data