Final answer:
A fallacy of incomplete evidence in an argument from authority happens when the arguer fails to consider all relevant evidence, which is a kind of fallacy of weak induction. The correct option is b.
Step-by-step explanation:
A fallacy of incomplete evidence is committed in an argument from authority when the arguer fails to consider all relevant evidence. This type of fallacy falls under the category of fallacies of weak induction, which happens when the evidence used is relevant, but too weak to support the conclusion.
An argument from authority may indeed present an expert's opinion, but if the argument ignores or omits other relevant evidence, the reasoning is flawed because it does not fully justify the conclusion with all available information.
This is different from using a biased source, which would imply the source itself is not credible, or appealing to popular opinion, which is a different kind of fallacy altogether known as ad populum. Relying on statistical data alone does not necessarily introduce a fallacy unless this data is also incomplete or irrelevant.
Hence, Option b is correct.