What must a player do if they cannot find an unmarked version of a card they need to replace?

In a tournament setting, the integrity of the game and the ability to accurately identify and track cards is paramount. When a player cannot find an unmarked version of a card they need to replace, replacing it with basic lands is the appropriate action. Basic lands are universally recognized and do not carry the same concerns as other types of cards that may have unique markings or characteristics that could give a player an unfair advantage or lead to confusion about card identification.

Using basic lands in such situations maintains the game's integrity and ensures consistency within a player’s deck, as these types of cards are readily available and distinctly identifiable. This approach aligns with the rules set forth to prevent any potential improprieties associated with marked cards and ensures a fair playing environment.

The other options do not adhere to the guidelines provided in tournament rules, as they may lead to potential issues of card identification and fairness in matches. By utilizing basic lands, players are fulfilling the requirements of maintaining a fair and regulated play environment without introducing additional complications.