Factor;then Use Fundamental Identities to Simplify the Expression Below and Determine

Multiple Choice

Factor;then use fundamental identities to simplify the expression below and determine which of the following is not equivalent.​ $\cot ^ { 2 } \alpha - \cot ^ { 2 } \alpha \cos ^ { 2 } \alpha$

A) ​ $\cos ^ { 2 } \alpha$
B) ​ $\sin ^ { 2 } \left( \frac { \pi } { 2 } - \alpha \right)$
C) ​ $1 - \sin ^ { 2 } \alpha$
D) ​ $\cot ^ { 2 } \alpha$
E) ​ $\frac { 1 } { \sec ^ { 2 } \alpha }$