A $$0.500\,\mathrm{g}$$ mixture of calcium carbonate and calcium oxide was strongly heated to produce a non-combustible gas. If the weight of the residue obtained on heating is found to be $$0.434\,\mathrm{g}$$, the percentage of calcium oxide in the mixture is

A

$$70\%$$

B

$$30\%$$

C

$$35\%$$

D

$$60\%$$