"Your Cleaning Team" is a company that provides house cleaning services in major urban and suburban areas. Marketers at Your Cleaning Team 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 it on to their friends and colleagues. The marketers at Your Cleaning Team are using $\_\_\_\_\_\_\_\_.$

a$.$ Rich media ads

b$.$ C$2$b marketing

c$.$ Viral marketing

d$.$ Content sponsorship

e$.$ A marketing website