The discontinuity is removable if by reducing the fraction that discontinuity doesn't continue to exist as a discontinuity.
Example of, (x-1)/(x-1) has a a discontinuity at x=1 and it's removable because the fraction reduces to 1 which doesn't have a discontinuity at x=1.
Example not of, (x-1)/(x-2) has a discontinuity at x=2 and it is not removable because we can't get rid of the x-2 factor in the denominator.
The first choice has a discontinuity at x=-1 and it is removable because x^2-x-2=(x-2)(x+1) and the x+1's will cancel on top and bottom making the point at x=-1 a removable discontinuity.
