How to select answer.id using queryobjects?

Content

Running queryobjects on Answer is too slow so I decided to just get the IDs.

But when running the query I get INVALID_REQUEST, Selected Column is not an object: ID

What is the best way to do this? (C#)

Code Snippet

             
query = "select Answer.id from Answer where Answer.CustomFields.c.blah like '%blah%'"

QueryResultData[] queryObjects = client.QueryObjects(cih, query, null, 10000);