(C) $-\tan^2 A$
$$\frac{1-\tan^2 A}{1-\cot^2 A} = \frac{1-\tan^2 A}{1-\dfrac{1}{\tan^2 A}} = \frac{1-\tan^2 A}{\dfrac{\tan^2 A -1}{\tan^2 A}} = \frac{(1-\tan^2 A)\cdot\tan^2 A}{-(1-\tan^2 A)} = -\tan^2 A$$
Examiners expect you to show the simplification step (replace $\cot^2 A = \frac{1}{\tan^2 A}$), then cancel the common factor $(1-\tan^2 A)$. Note this is different from Exercise 8.3 Q3(iv) which has plus signs; here the minus signs flip the denominator's sign, giving the negative answer. Always justify MCQ choices with at least one working step.