Final answer:
Mapmakers include deliberate errors in their maps to protect their intellectual property and spot copyright infringement. These errors, like 'trap streets', are not meant to mislead but to guard against unauthorized copying.
Therefore, option C is correct.
Step-by-step explanation:
The reason mapmakers include mistakes in their work is to protect their intellectual property and to easily identify and prove cases of copyright infringement. When a unique and intentional error is incorporated into a map, it serves as a 'trap street' or a 'paper town', which can be used to detect if someone else has copied the map without permission. These deliberate errors do not aim to mislead the public but are there to safeguard the mapmaker's work against unlawful reproduction and use by competitors.