When an unknown hydrocarbon A (molecular formula C8H16), is exposed to Cl2, the Cl2 rapidly disappears, and a mixture of two products, B and C, is isolated. B and C each have molecular formula C8H16Cl2. The mixture of B and C is optically inactive, but when B and C are separated from each other, the isolated compounds are each optically active. When A is treated with OsO4, followed by NaHSO3, a single product D (C8H18O2) can be isolated. D is optically inactive. Finally, when A is exposed to O3, followed by H2O2, the only product isolated is 2-butanone (structure shown below). Given this information, propose structures for the unknown compounds A, B, C, and D. Write your answers in the appropriate boxes in the reaction scheme provided below.