How many relational database engines does RDS currently…

How many relational database engines does RDS currently support?

A.
Three: MySQL, Oracle and Microsoft SQL Server.

B.
Just two: MySQL and Oracle.

C.
Six: Amazon Aurora, Oracle, Microsoft SQL Server, PostgreSQL, MySQL and MariaDB.

D.
Just one: MySQL.

Explanation:
Amazon RDS provides you six familiar database engines to choose from, including Amazon

Aurora, Oracle, Microsoft SQL Server, PostgreSQL, MySQL and MariaDB.
https://aws.amazon.com/rds/?nc1=h_ls