A penetration tester recently performed a social-engineering attack in which the tester found an employee of the target company at a local coffee shop and over time built a relationship with the employee. On the employee's birthday, the tester gave the employee an external hard drive as a gift.
Which of the following social-engineering attacks was the tester utilizing?

A. Phishing
B. Tailgating
C. Baiting
D. Shoulder surfing