JEE Main · 2020 · 04 Sep 2020 · Shift 1 · Chapter_pending

The starting ketone is treated with the Grignard reagent $\mathrm{CH}{}_3\mathrm{MgBr}$ and then hydrolysed, and the product [B] is examined for stereocentres, a stereocentre being any $s{p}^3$ carbon carrying four different groups. Going through the carbons of [B], four of them meet this condition, so [B] has four chiral centres.