What is one feature that prevents erasure on a prescription?

The correct answer is that a uniform background color on a prescription serves as a feature that helps prevent erasure. This characteristic makes it more difficult for anyone to alter the prescription once it has been written. A uniform background color ensures that any alterations would be immediately noticeable, helping to maintain the integrity of the prescription by making tampering obvious.

While security features are also a common method to enhance the validity of a prescription, they often involve various measures like watermarks or specific inks that may not directly prevent erasure in the same visible manner as a consistent background. Quantity check boxes are practical for indicating specific amounts but do not serve any purpose in preventing alteration. Unsigned forms lack the necessary authentication and validity, making them ineffective in preventing tampering or erasure, rather than contributing to protection against changes.