Concept:The function is discontinuous at x=1 when the limit as x→1 does not equal the function value at x=1.Explanation:For x=1, the expression is 1−x1−xm, which is a 00 indeterminate form as x→1.Apply L'Hôpital's rule: differentiate numerator and denominator with respect to x.limx→11−x1−xm=limx→1−1−mxm−1=m.For continuity at x=1, we require limx→1f(x)=f(1).Given f(1)=2m−1, so m=2m−1 implies m=1.Thus the function is continuous only when m=1.For discontinuity, m=1.Answer:Option D: m=1.