If $$\sin \theta + \cos \theta = m$$, then $$\sin^{6} \theta + \cos^{6}\theta$$ equals

A

$$\frac{3(m^{2} + 1)}{4}$$

B

$$\frac{3(m^{2} - 1)}{4}$$

C

$$1-\frac{3(m^{2} + 1)}{4}$$

D

$$1-\frac{3(m^{2} + 1)^{2}}{4}$$