Which of the following should a software developer use to BEST prevent unauthorized reproduction of software?

A watermark is a visible or invisible mark used to identify ownership of digital media or documents, but it does not legally prevent reproduction of software code itself.

Copyright automatically applies to original works of authorship, including software code, upon its creation, granting the owner exclusive rights to reproduce, distribute, and modify the work. This legal protection is the primary mechanism to prevent unauthorized copying and distribution of software.

A patent protects inventions, processes, or designs, providing exclusive rights for a limited period, but it is typically used for specific algorithms or functionalities, not the software code as a whole which is covered by copyright.

A trademark protects names, logos, and symbols used to identify goods or services and distinguish them from others, but it does not prevent the reproduction of the underlying software.