Ether Inc, an Electronics Manufacturer, Offers Free T-Shirts with the Company's

Ether Inc., an electronics manufacturer, offers free T-shirts with the company's logo on them free of charge to its customers. Ether believes that this will help promote the company's products and attract more customers. This is an example of:

A) in-store advertising.
B) specialty advertising.
C) public relations enhancement.
D) guerrilla marketing.
E) product placement.