For what values of x does f(x) = 2x + 4 sin x have a horizontal tangent line? Choose the correct answer below. O A. X= 3 -+ kit and x = 3 -+ kit, where k is any integer 11x XB. X= - + Kit and x = 6 6 + kit, where k is any integer *C. X= 3 + 2kit and x = 3 - + 2kit, where k is any integer OD. X= 6 + 2kit and x = 4 6 + 2kit, where k is any integer