$$\frac{\left(1+\sec\theta\csc\theta\right)^{2}\left(\sec\theta-\tan\theta\right)^{2}\left(1+\sin\theta\right)}{\left(\sin\theta\sec\theta\right)^{2}+\left(\cos\theta\csc\theta\right)^{2}}, 0^\circ < \theta < 90^\circ$$ is equal to:

A

$$1-\cos\theta$$

B

$$1-\sin\theta$$

C

$$\cos\theta$$

D

$$\sin\theta$$