Final answer:
The feature that allows the Big SQL user to securely access data in Hadoop on behalf of another user is A. Impersonation.
Step-by-step explanation:
The feature that allows the Big SQL user to securely access data in Hadoop on behalf of another user is Impersonation. Impersonation allows a Big SQL user to assume the identity of another user, granting them access to their data without revealing their own credentials. This is useful in scenarios where a user needs to access data on behalf of another user, such as when running queries or performing operations on sensitive data.
For example, let's say User A has access to sensitive data stored in Hadoop, but User B needs to analyze that data using Big SQL. Instead of providing User B with direct access to the data, User A can use impersonation to grant User B temporary access to the data without compromising User A's credentials.
It is important to note that impersonation is done within the confines of Authorization. Authorization determines what actions a user is allowed to perform, while impersonation allows a user to perform those actions on behalf of another user.