Choose the correct statement about the compounds $\mathrm{A}, \mathrm{B}$ and $\mathrm{C}$.
(a) $\mathrm{A}$ and $\mathrm{B}$ are identical
(b) $\mathrm{A}$ and $\mathrm{B}$ are diastereomers
(c) A and $\mathrm{C}$ are enantiomers
(d) A and B enantiomers