Unable to retrive Severity of a workitem from TFS programatically

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C#

I'm trying to retrieve details of work items from TFS as below

tpc = new TfsTeamProjectCollection(new Uri(tfsCollection));
           string query = @"Select [State], [Title],[Severity] From WorkItems Where [Work Item Type] = 'Bug'  AND [Area Path] = '" + areaPath + "'  AND  [Iteration Path] = '" + iterationPath + "'  AND [Team Project]='" + projectName + "'";
           workItemStore = (WorkItemStore)tpc.GetService(typeof(WorkItemStore));

I'm able to retrieve State and Title of the workitem but not Severity.

There is no property for Severity in WorkItemCollection.

 WorkItemData workItemData = new WorkItemData();
workItemData.WorkItemTitle = queryResults[i].Title;
workItemData.WorkItemState = queryResults[i].State;

How can we retrieve Severity and Priority of the workitem from TFS programmatically?
It would be great if you can help me out..