Answer: 0.2 M
Step-by-step explanation:
Since the original HCl solution was 0.2 M, and the student just poured 40 mL of the original 100 mL solution in a beaker without adding any extra liquid in it (either solute or solvent). so the concentration will not change. Concentration changes only when the amount of either solute (HCl) or solvent (water) changes