Salesforce ActivityHistories ActivityType返回垃圾

Question

我正在运行此查询以获取与商机相关的所有活动：

SELECT (SELECT Id, Subject, ActivityType, ActivityDate, OwnerId, CreatedBy.Name,Description FROM ActivityHistories) FROM Opportunity

这就是我得到的：

...
"records": [
                {
                    "attributes": {
                        "type": "ActivityHistory",
                        "url": "/services/data/v28.0/sobjects/ActivityHistory/00Ti000000B72QWEAZ"
                    },
                    "Id": "00Ti000000B72QWEAZ",
                    "Subject": "test Call 2",
                    "ActivityType": "1_",
                    "ActivityDate": "2011-07-05",
                    "OwnerId": "005i00000013T0TAAU",
                    "CreatedBy": {
                        "attributes": {
                            "type": "User",
                            "url": "/services/data/v28.0/sobjects/User/005i00000013T0TAAU"
                        },
                        "Name": "John Fiedler"
                    },
                    "Description": "test comment"
                },
...

ActivityType字段为“1_”，它应该是“Call”，“Event”等的选项列表。任何建议？