This is a numerical-answer question. The correct answer is shown below.
[Solution by Dr. Abubacker] 0.1 M × 40 mL = 4 mmol HCl neutralises 2 mmol of excess Ca(OH)₂. CO₂ consumed exactly half of the initial Ca(OH)₂, so the amount consumed equals the excess: 2 mmol. Hence n(CO₂) = 2 mmol and, at 1 atm and 273 K, V = 2 × 22.4 = 44.8 cm³ ≈ 45. Answer: 45.