Ideal Gas Law Governs Gas Volume Steps:

• Recall PV = nRT for fixed n; V ∝ T/P.
• To decrease V, increase P or decrease T (or both).
• Evaluate each option: identify if pressure change alone decreases V, and if temperature change alone decreases V.
• Select option where both changes independently decrease V.

Why B is correct:

• Increasing pressure compresses gas (V decreases per Boyle's Law: V ∝ 1/P); decreasing temperature slows molecules (V decreases per Charles's Law: V ∝ T).

Why the others are wrong:

• A: Decreasing pressure expands gas (increases V).
• C: Both decreasing pressure and increasing temperature expand gas (increase V).
• D: Increasing temperature expands gas (increases V).

Final answer: B