Aldehydes Ketones And Carboxylic Acids

" P " is an optically active compound with molecular formula $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}$. When ' P ' is treated with 2, 4-dinitrophenylhydrazine, it gives a positive test. However, in presence of Tollens reagent, " P " gives a negative test.
Predict the structure of " P ".