Elizabeth Bennett challenges the cultural norms of Regency England primarily through her refusal of Mr. Collins' marriage proposal, which is significant given that he is an eligible man with the potential to inherit her family’s estate. Her rejection of the marriage indicates her defiance against the societal expectation for women to marry for security and status, rather than for love or personal choice. Therefore, the best answer is:
- by rejecting marriage to an eligible man who will inherit her family’s estate.