What conceptual error has the researcher made in declaring the entire geologic timescale invalid based on the analysis of an obsidian arrowhead?
a) Misinterpretation of the ratio of 40Ar/40K
b) Assuming the age of the arrowhead represents the age of the Earth
c) Ignoring the possibility of natural processes altering isotopic ratios
d) Failing to consider alternative methods for dating geological formations
