What type of documents does the USPTO provide free of charge to prosecutors?

The correct choice revolves around the specific types of documents the USPTO makes available to prosecutors free of charge. Certified copies of trademark registration certificates are essential in legal contexts, particularly during enforcement actions, where proof of trademark ownership and rights is necessary. These certified copies serve an official purpose by confirming the status of a trademark and are often used in court or administrative proceedings.

In contrast, trademark application forms are readily accessible to everyone and do not require any payment, but they are not specifically designated for prosecutors. Patent grants pertain to a different area of intellectual property and are not relevant in the context of trademarks. Copyright application forms also relate to a distinct field of intellectual property, separate from both patents and trademarks.

Thus, the focus on certified copies reflects a specific utility in legal proceedings and enforcement related to trademarks, making it the best answer in this context.