Answer
$$1=\sin^2 x+\cos^2 x$$
We would pick $\text{A}$ as the answer here.
Work Step by Step
$$1$$
According to the Pythagorean Identities, we have
$$\sin^2\theta+\cos^2\theta=1$$
Therefore, $$1=\sin^2 x+\cos^2 x$$
We would pick $\text{A}$ as the answer here.