In the context of data warehousing and database management, ETL processes are crucial for transferring data from operational databases to analytical databases. Considering the roles of Online Transaction Processing $($OLTP$)$ and Online Analytical Processing $($OLAP$)$ systems, what is the primary role of ETL?

A$)$

ETL's main role is to facilitate real$-$time data analysis directly within OLTP systems without the need for data transformation

B$)$

ETL processes extract data from OLAP systems to be transformed and loaded into OLTP systems for operational reporting

C$)$

The primary role of ETL is to extract data from various OLTP systems, transform this data to ensure consistency, and then load it into an OLAP system for complex queries and analysis

D$)$

ETL primarily enhances the transaction speed of OLTP systems by streamlining data entry and retrieval processes

E$)$

ETL is used to duplicate data within OLTP systems to create backups without affecting the OLAP systems