Concept: A Union Catalogue is a combined catalogue showing the holdings of more than one library. It is useful for resource sharing, inter-library loan and locating documents.
Step 1: Understand the purpose of a Union Catalogue.
Before preparing a union catalogue, the purpose must be clear. It may be prepared for locating books, avoiding duplication or supporting inter-library loan.
\[
A = \text{Purpose of the Union Catalogue}
\]
Step 2: Need for catalogue code.
Libraries participating in a union catalogue should follow a common catalogue code. This maintains uniformity in entries.
\[
C = \text{Catalogue code to be followed}
\]
Step 3: Need for arrangement of entries.
The arrangement of entries must also be decided so that users can search the catalogue easily.
\[
E = \text{Arrangement of entries}
\]
Step 4: Reject unrelated items.
List of prices of books and list of addresses of publishers are not basic prerequisites for preparing a union catalogue.
Therefore, the correct set is:
\[
A,\ C,\ E
\]