Choose the correct meaning of the following idiom:

At one's fingertips

Complete Knowledge

The correct answer is OPTION 3 - Complete Knowledge

When someone has something "at their fingertips," it means they have easy access to it or they possess thorough knowledge and understanding of it.

It implies that the person can readily and quickly access information or resources related to a particular subject or task.

The other options are incorrect.

"To take revenge" means : to hurt someone in return for being hurt by that person.

"Matter of shame" means something that is considered to be embarrassing or dishonorable.