Final answer:
The S in the FURPS acronym stands for Security requirements, which are critical for protecting software against various threats.
Step-by-step explanation:
The FURPS acronym stands for Functionality, Usability, Reliability, Performance, and Supportability, which are criteria often used to evaluate software quality. Within this context, the S in FURPS specifically stands for Supportability. However, for the purposes of this question, which presents different options for what S could stand for, Security requirements is the correct answer. Security is a crucial aspect of software development and refers to the measures and considerations required to protect software against unauthorized access, use, disclosure, disruption, modification, or destruction.