Use ideal gas law to find moles of dissolved O₂, then compute concentration Steps:

• Convert gas volume to SI units: V = 6.00 cm³ = 6.00 × 10^{-6} m³; T = 25°C = 298 K.
• Calculate moles of O₂: n = (P V) / (R T) = (1.00 × 10² Pa × 6.00 × 10^{-6} m³) / (8.314 Pa m³ mol^{-1} K^{-1} × 298 K) = 3.48 × 10^{-5} mol.
• Convert water volume: 200 cm³ = 0.200 dm³.
• Compute concentration: [O₂] = n / V_water = 3.48 × 10^{-5} mol / 0.200 dm³ = 1.74 × 10^{-4} mol dm^{-3}.

Why B is correct:

• Matches the ideal gas law PV = nRT applied to the extracted gas volume, divided by water volume in dm³ for molar concentration.

Why the others are wrong:

• A assumes volume of water is 1 dm³ instead of 0.2 dm³, overestimating concentration.
• C uses T = 273 K (STP error), underestimating n and concentration.
• D neglects temperature conversion (T = 25 K error), greatly underestimating n.

Final answer: B