Question

both were thoroughgoing materialists, not in prizing possessions but in holding that matter alone provided the underpinnings of the world.
in this sentence, thoroughgoing means:
without qualification
possessing an education (especially having more than average knowledge)
excessively conventional and unimaginative and hence dull
given to or characterized by presenting misleading arguments

Explanation:

The word "thoroughgoing" in the context of the sentence means "without qualification". The sentence is emphasizing that both individuals were complete or unqualified materialists, not in terms of prizing possessions but in their belief that matter alone provided the underpinnings of the world. The other options do not fit the context of the sentence. "Possessing an education" is about knowledge, which is not relevant here. "Excessively conventional and unimaginative" and "presenting misleading arguments" also do not match the idea of being complete or unqualified materialists.

Answer:

without qualification