In the reaction, $\mathrm{CH}_{3} \mathrm{CHO}+\mathrm{HCN} \longrightarrow \mathrm{CH}_{3} \mathrm{CH}(\mathrm{OH}) \mathrm{CN}$
a chiral centre is produced. This product would be
(a) racemic mixture
(b) meso compound
(c) dextrorotatory
(d) laevorotatory