[{"id": 1, "type": "short_answer", "skill": "computation", "question": "Calculate: 21 + 47", "difficulty": "medium", "explanation": "Add systematically.", "needs_review": false, "correct_answer": "68"}, {"id": 2, "type": "multiple_choice", "skill": "properties", "options": ["Associative property", "Commutative property", "Identity property", "Distributive property"], "question": "Which property states a+0=a?", "difficulty": "easy", "explanation": "The identity property of addition states that adding 0 to any number gives that number.", "needs_review": false, "correct_answer": "Identity property"}, {"id": 3, "type": "short_answer", "skill": "computation", "question": "Calculate: 2 × 8", "difficulty": "medium", "explanation": "Multiply: 2×8=16", "needs_review": false, "correct_answer": "16"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 4 × 15", "difficulty": "medium", "explanation": "Multiply: 4×15=60", "needs_review": false, "correct_answer": "60"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 13 × 5", "difficulty": "medium", "explanation": "Multiply: 13×5=65", "needs_review": false, "correct_answer": "65"}]