Clenzo is a company that provides house cleaning services in major urban and suburban areas. Marketers at Clenzo developed a short, humorous video promoting the company's services and hope that customers who see the video will be so entertained that they will pass the video on to their friends and colleagues. The marketers at Clenzo are using techniques to facilitate $\_\_\_\_\_\_\_\_.$

$$

direct$-$mail marketing

display advertising

viral marketing

contextual advertising

catalog marketing