{
    "meta_info": {
        "case_id": "Q26",
        "bench_subset": "NeuroBench-Core",
        "difficult": 1.0,
        "original_dataset": "Core_QA",
        "references": "R9,R10"
    },
    "agent_input": {
        "data_path": "",
        "instruction": "This is a standalone EEG/BCI knowledge multiple-choice question. No EEG data file is needed. Please answer by selecting exactly one option: A, B, C, or D.\n\nQuestion: Mu rhythm can be confused with posterior alpha. Which clue helps distinguish it?\nA. Mu appears only in the occipital region and only because of visual eye closure.\nB. Mu has a fixed frequency of 50 Hz.\nC. Mu is essentially an ECG artifact.\nD. Mu is more central sensorimotor and is often suppressed by movement or motor imagery."
    },
    "eval_config": {
        "parser_prompt": "### ROLE\nYou are a precise JSON Extraction Engine for multiple-choice EEG/BCI QA responses. Your sole task is to extract the final selected answer option.\n\n### TASK\nExtract the final selected option from the agent report.\n\n### STRICT CONSTRAINTS (MANDATORY)\n1. Output ONLY a valid JSON object.\n2. DO NOT include Markdown code blocks.\n3. DO NOT include any conversational text, explanations, or units.\n4. The key must be EXACTLY \"selected_option\".\n5. The value must be one of \"A\", \"B\", \"C\", \"D\", or null.\n6. If multiple options are mentioned, extract only the final answer option.\n7. If the selected option is missing or unclear, return {\"selected_option\": null}.\n\n### OUTPUT TEMPLATE\n{\"selected_option\": <string|null>}",
        "metrics": [
            {
                "metric_id": "qa_option_accuracy",
                "type": "categorical_check",
                "target_key": "selected_option",
                "weight": 100,
                "params": {
                    "gt_value": "D"
                }
            }
        ]
    }
}