The online data entry control called preformatting is A. A program initiated prior to regular input to discover errors in data before entry so that the errors can be corrected. B. A check to determine if all data items for a transaction have been entered by the terminal operator. C. A series of requests for required input data that requires an acceptable response to each request before a subsequent request is made. D. The display of a document with blanks for data items to be entered by the terminal operator.

The online data entry control called preformatting simply refers to the display of a document with blanks for data items to be entered by the terminal operator.

Option A is incorrect as it isn't the program that's initiated by a user before regular input in order to discover errors in data before entry so that the errors can be corrected.

Option B is incorrect as it isn't a check to determine if all data items for a transaction have been entered by the terminal operator.

Option C is incorrect as it isn't a series of requests for the required input data which requires an acceptable response to each request before a subsequent request is made.

Therefore, the correct option is D.