The ester shown is heated with aqueous $\mathrm{NaOH}$ and then acidified. Which structure is the chiral alcohol obtained?

The compound is (R)-sec-butyl acetate. Saponification proceeds by attack of hydroxide on the carbonyl carbon and cleavage of the acyl-oxygen bond; the C-O bond at the stereocentre is never broken, so the configuration is retained and (R)-butan-2-ol forms (the priority order O > ethyl > methyl > H is unchanged). Inversion (the enantiomer) would require attack at the alkyl carbon, which does not happen.