Which input style cannot be combined with @@?

The correct answer indicates that both formatted input and list input styles can be used with the @@ modifier. The @@ operator is used in SAS to allow for multiple records to be read on the same line, effectively keeping the input stream open until the end of the data line is reached or a specific logical condition is met.

In the case of list input, values are read in as they appear in a line without any specific formatting applied. This is particularly flexible for reading raw data where values are separated by spaces. The use of @@ here allows for continuous reading of values until the end of the line is reached, thus enabling efficient processing of multiple records.

Similarly, formatted input can also utilize @@, although it may involve more complex formats to specify how each piece of data should be read, such as specifying the length and type of input. By combining formatted input with @@, SAS can interpret data more accurately if the structure of the incoming data requires specific formatting rules (e.g., dates, numerical values).

Therefore, stating that both input styles can be combined with @@ reflects the versatility of SAS input methods, which enhances data management capabilities in different scenarios.