Which type of audience appeals does the statement show? Four out of five doctors agree that honey and cinnamon tablets are effective against the common cold.

It shows the appeal to ethos.

Appealing to ethos is appealing to the credibility of the person saying something. In this case, you talk about doctors and since the advice is about health, doctors are good for giving health advice, so they gain credibility as health experts when they say something like that more than if a coal miner said it, for example.