What is the general form of the equation for the given circle centered at O(0, 0)?
a. x^2 + y^2 + 41 = 0
b. x^2 + y^2 − 41 = 0
c. x^2 + y^2 + x + y − 41 = 0
d. x^2 + y^2 + x − y − 41 = 0