A consultant is hired to do physical penetration testing at a large financial company. In the first day of his assessment, the consultant goes to the company`s building dressed like an electrician and

A man trap is a physical security control consisting of two interlocked doors that allow only one person through at a time - it is a countermeasure against tailgating, not an attack technique.

Tailgating (also called piggybacking) is a physical intrusion technique where an unauthorized person exploits the courtesy or inattention of an authorized user to pass through a secured door immediately behind them without using any credential. In this scenario the consultant deliberately positioned himself behind the employee and entered the restricted area by following closely through the access gate, matching the textbook definition of this attack.

Shoulder surfing involves covertly observing a target's screen, keyboard, or PIN pad to steal sensitive information, not physically following someone through a secured doorway.

Social engineering is a broad umbrella term covering many manipulation techniques; tailgating is the specific physical attack demonstrated here and is the more precise and correct answer.