Step-by-step explanation:
The statement "my friend is an expert for 20 years" is an example of ethos, which is a rhetorical appeal that relies on the credibility or trustworthiness of the speaker or the source of information. By stating that their friend is an expert for 20 years, the speaker is implying that their friend has a long history of experience and knowledge in a particular field, which lends credibility to their expertise. This can be seen as an attempt to persuade the listener to trust the friend's knowledge and opinions.