Answer:
Publicity.
Step-by-step explanation:
It is common to find this kind of advertisment when you are watching tv. You will find some announcements that recommend products like shampoo, toothpaste, some food, etc. And all these products have something in common. There is always some people recommending these products.
For example in this kind of advertisment people would say:
-"Nine out of ten cats prefer Whiskas."
So Vets recommend people to buy "Whiskas".
-"Four out of five dentists recommend Colgate toothpaste."
So dentists recommend people to buy "Colgate".