To open a new posting period for material master records in SAP S/4HANA Cloud Public Edition, specific apps are used to manage posting periods effectively. Below is an explanation of the correct answers:

By using the Manage Product Master Data app (C):TheManage Product Master Dataapp allows users to maintain material master records, including extending them to new posting periods. This ensures that materials are available for transactions in the new period.

By using Manage Posting Periods app (D):TheManage Posting Periodsapp is used to define and control the opening and closing of posting periods for financial and material transactions. It ensures that the system allows postings only within valid periods.

By closing the current period using the Close Periods app (A):Closing the current period does not automatically open a new one. Separate steps are required to define and activate the new period.

By triggering a background job using Close Period for Product Master app (B):There is no standard app called "Close Period for Product Master" in SAP S/4HANA Cloud Public Edition. This option is invalid.