10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount HCl solution (the same solution as before) required to neutralise it will be:

The correct option is D 16 mL
Reaction of HCl and NaOH is:
NaOH + HCl → NaCl + H₂O
1 mol of NaOH is neutralized by 1 mol of HCl.
If 10 mL of NaOH is neutralized by HCl = 8 mL
1 mL of NaOH will neutralize by HCl = 8/10 mL
20 mL of NaOH for neutralization will require HCl = 0.8 × 20 mL = 16 mL
So, the correct option is D