The rate law for the reaction $2 \mathrm{A} \rightarrow \mathrm{B}$ is second order in A. Figure $\mathrm{P} 13.3$ represents samples with different concentrations of $\mathrm{A}$; the red spheres represent molecules of
A. In which sample will the reaction $A \rightarrow B$ proceed most rapidly?
(FIGURE CANNOT COPY)