\sin^2 \theta and \cos^2 \theta reminds use of Pythagorean Theorem.

Factoring out the common factor of the two terms, the sum of trig terms becomes constant 1. Then, the value of the expression is computed as

1-2\sin^2 \theta -2\cos^2 \theta=1-2(\sin^2 \theta +\cos^2 \theta)=1-2=-1

Therefore,

The right choice B