{
  "pages": [
    {
      "name": "page1",
      "elements": [
        {
          "type": "matrixdropdown",
          "name": "question1",
          "columns": [
            {
              "name": "Column 1",
              "cellType": "radiogroup",
              "showInMultipleColumns": true,
              "choices": [
                {
                  "value": "c1",
                  "text": "Column 1"
                },
                {
                  "value": "c2",
                  "text": "Column 2"
                },
                {
                  "value": "c3",
                  "text": "Column 3"
                }
              ],
              "allowClear": true
            }
          ],
          "detailElements": [
            {
              "type": "paneldynamic",
              "name": "question3",
              "templateElements": [
                {
                  "type": "comment",
                  "name": "question2"
                }
              ],
              "addPanelText": "Add more",
              "templateQuestionTitleLocation": "left"
            }
          ],
          "detailPanelMode": "underRow",
          "choices": [
            1,
            2,
            3,
            4,
            5
          ],
          "rows": [
            "Row 1",
            "Row 2"
          ]
        }
      ]
    }
  ]
}