To solve this question, the user needs to have knowledge about ADO.NET and the different types of DataAdapter objects available in ADO.NET.

Now, let's go through each option to determine which one is not an ADO.NET DataAdapter object:

A. OleDbDataAdapter: This is a valid ADO.NET DataAdapter object. It is used to retrieve and update data from and to an OleDb data source.

B. SQLDataAdapter: This is also a valid ADO.NET DataAdapter object. It is used to retrieve and update data from and to a SQL Server database.

C. QueryDataAdapter: This option is not a valid ADO.NET DataAdapter object. There is no such class as QueryDataAdapter in ADO.NET.

D. Both a and b: This option is incorrect because OleDbDataAdapter and SQLDataAdapter are both valid ADO.NET DataAdapter objects. The correct answer cannot be D.

E. All of the above: This option is incorrect because the correct answer is C. QueryDataAdapter is not a valid ADO.NET DataAdapter object.

Therefore, the correct answer is:

C. QueryDataAdapter