A student added 0.20 g of calcium carbonate powder to ${\text{100 c}}{{\text{m}}^{\text{3}}}$ of ${\text{1.0 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}$ hydrochloric acid (an excess) and measured the volume of the gas that was evolved. The graph of the results is shown below.

Which graph would be obtained if 0.20 g of calcium carbonate powder is added to ${\text{100 c}}{{\text{m}}^{\text{3}}}$ of ${\text{0.5 mol}}\,{\text{d}}{{\text{m}}^{ - 3}}$ hydrochloric acid (an excess)?

B