Final answer:
An argument can be valid but not necessarily good if it has false or irrelevant premises, such as in the case of a false dichotomy.
Step-by-step explanation:
While an argument being valid implies that if the premises were true, the conclusion would necessarily be true, it does not necessarily mean we have a good argument. What makes an argument good also depends on the truthfulness and relevance of its premises. A valid argument with untrue or irrelevant premises may not be good, as it leads to a conclusion not supported by fact. This is seen in arguments that contain a false dichotomy, where it is incorrectly assumed that there are only two possibilities, neglecting other viable options. Therefore, the correct answer is a) true.