Anecdotal evidence: A. is often concrete, vivid, and memorable. B. tends to influence people. C. is fundamentally flawed and unreliable. D. is all of the above.

Anecdotal evidence is a type of informal evidence that is based on personal experiences, observations, or stories. It is often presented in a conversational manner, and while it lacks scientific rigor, it can be quite influential due to its emotional impact and relatability.

Now that we understand anecdotal evidence, let us examine the various options provided: A. "is often concrete, vivid, and memorable" - This is true since anecdotal evidence tends to be based on personal experiences, which are usually specific and emotionally charged, making them easy to remember. B. "tends to influence people" - This is also true, as people are generally more persuaded by personal stories and experiences than by abstract statistics or scientific data. C. "is fundamentally flawed and unreliable" - While anecdotal evidence can offer insight and add context to an issue, it is often subject to various biases and limitations, making it unreliable as a sole basis for making conclusions or decisions. D. "is all of the above" - This option indicates that all the characteristics listed above apply to anecdotal evidence.

After analyzing each of the options, we can conclude that option D, "is all of the above," is the correct answer to this question. It encompasses all aspects of anecdotal evidence, including its vividness, influence, and inherent unreliability.