Correct answer is C.
y = 4x – x
This is a parabola with negative co-efficient of x2, i.e., it’s a downward parabola.
So, area A enclosed is the area of the peak of the parabola above the x – axis.
We need to find the bounds of this peak.
Now, at the point where the peak starts/ends, y = 0,
i.e., 4x – x2 = 0
⇒ x(4 – x) = 0
⇒ x = 0 or x = 4