**Core Concept**
SIRS (Systemic Inflammatory Response Syndrome) is a clinical condition characterized by a systemic inflammatory response to a variety of insults, including infections, trauma, burns, and pancreatitis. The SIRS criteria are used to diagnose SIRS and include two or more of the following: body temperature > 38°C or 90 beats per minute, respiratory rate > 20 breaths per minute, or white blood cell count > 12000 cells/μL or < 4000 cells/μL. **Why the Correct Answer is Right** The correct answer is **White blood cell count < 4000 cells/μL**. This is because the SIRS criteria require an elevated white blood cell count, not a decreased one. In fact, a decreased white blood cell count (leukopenia) is more characteristic of sepsis or septic shock, which is a more severe condition that builds upon SIRS. **Why Each Wrong Option is Incorrect** **Option A:** This option is not provided as the question was incomplete. **Option B:** This option is not provided as the question was incomplete. **Option C:** This option is not provided as the question was incomplete. **Clinical Pearl / High-Yield Fact** It's essential to remember that SIRS is a non-specific condition that can result from various causes. A diagnosis of SIRS should prompt further investigation to identify the underlying cause, which may require additional diagnostic tests or interventions. **Correct Answer: D.**