[{"id": 1, "type": "short_answer", "skill": "computation", "question": "Calculate: 39 + 11", "difficulty": "medium", "explanation": "Add systematically.", "needs_review": false, "correct_answer": "50"}, {"id": 2, "type": "multiple_choice", "skill": "properties", "options": ["Distributive property", "Associative property", "Identity property", "Commutative 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: 5 × 8", "difficulty": "medium", "explanation": "Multiply: 5×8=40", "needs_review": false, "correct_answer": "40"}, {"id": 4, "type": "short_answer", "skill": "computation", "question": "Calculate: 4 × 10", "difficulty": "medium", "explanation": "Multiply: 4×10=40", "needs_review": false, "correct_answer": "40"}, {"id": 5, "type": "short_answer", "skill": "computation", "question": "Calculate: 18 × 4", "difficulty": "medium", "explanation": "Multiply: 18×4=72", "needs_review": false, "correct_answer": "72"}]