Concept:For a function to be continuous at a point, the value of the function at that point must equal its limit at that point.Explanation:Since f(x) is continuous on [0,2π], it is continuous at x=4π.Therefore, f(4π)=limx→4πf(x).Substitute: limx→4π4x−π1−tanx.As x→4π, both numerator and denominator tend to 0, so apply L'Hospital's rule.Differentiate numerator: dxd(1−tanx)=−sec2x.Differentiate denominator: dxd(4x−π)=4.Thus, f(4π)=limx→4π4−sec2x.At x=4π, sec2(4π)=2.So, f(4π)=4−2=−21.Answer:−21 (Option A).