gistfile1.txt

"questionA": {
      "type": "object",
      "properties": {
        "answer": {
          "type": "string",
          "minLength": 1,
          "enum": ["Yes", "No"]
        }
      }
    }

    "questionB": {
      "type": "object",
      "properties": {
        "answer": {
          "type": null,
        }

      }
    }
    
    
    "questions": {
              "type": "object",
              "properties": {
                "A": {"$ref": "#/definitions/questionA"},
                "B": {"$ref": "#/definitions/questionB"}
              },
              "if": {
                "properties" : {
                  "A": {"enum": ["Yes"]}
                }
              },
              "then": {
                "B": {
                  "type": "string",
                  ... etc
                }
              }