Which is a correct unit for expressing the rate of a reaction?

A.     ${\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{{\text{s}}^{ - 1}}$

B.     ${\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}{\text{s}}$

C.     ${\text{mol}}\,{\text{s}}$

D.     ${\text{mo}}{{\text{l}}^{ - 1}}\,{\text{d}}{{\text{m}}^{\text{3}}}{{\text{s}}^{ - 1}}$

A