Pure alpha-D-glucopyranose has specific rotation $+112.2^{\circ }$, the beta anomer $+18.7^{\circ }$ and the equilibrium mixture $+52.7^{\circ }$. Ignoring the open-chain form, the mole percent of the alpha anomer at equilibrium is

1. A36.4%
2. B52.7%
3. C47.3%
4. D63.6%