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Air bubbles act as a gas reservoir that equilibrates with the specimen and skews measured pO₂ and pCO₂ (e.g., atmospheric oxygen can falsely elevate pO₂). The most important immediate step after collection is to express visible air bubbles, cap the heparinized syringe securely, gently mix to prevent microclots, and transport rapidly per your lab’s policy (often on ice if analysis is delayed). Option B addresses these critical elements. Vigorous shaking (Option A) can hemolyze cells and introduce microbubbles. Transferring to a red-top tube (Option C) is inappropriate; blood gases are analyzed from the original heparinized syringe. Letting the sample sit at room temperature (Option D) allows ongoing cellular metabolism that alters pH, pCO₂, and pO₂. Additional best practices include avoiding prolonged tourniquet time for venous gases, ensuring correct patient oxygen settings are documented, and verifying analyzer readiness on arrival. Prompt, airtight handling preserves clinical accuracy for ventilator adjustments and acid–base management.