Working for question 15 MC should look like this:
At 25 degrees concentration is 8mg/L which is 80mg or 0.08g in 10L
n = m/M
= 0.08/32
= 2.5x10^-3 moles
At standard pressure 100kPa
V = n x Vn
= 2.5x10-3 x 24.79
= 0.061975L or 62mL
Therefore the answer is D