If $$\cos^2 A + \cos^4 A = 1$$​, then the value of the expression $$\sin A + \sin^2 A$$​ is:

Given​​

​$$\cos^2 A + \cos^4 A = 1 \tag{....1} \\\cos^4A = 1 - \cos^2A \\\cos^4A = \sin^2A \\\implies \sin A = \cos^2 A$$

​​We know the identity: 

​$$\sin^2 A = 1 - \cos^2 A \tag{......2}$$​​​​
Then: $$\sin^2 A = (\cos^2 A)^2 = \cos^4 A$$​​
Now, calculate the expression:
​$$\sin A + \sin^2 A = \cos^2 A + \cos^4 A$$​​
From given $$\quad \cos^2 A + \cos^4 A = 1$$​​
​$$\Rightarrow \sin A + \sin^2 A = 1$$​​
Correct answer is (b) 1.