answer is a. nora realizes that helmer will completely disapprove of her having borrowed money, so she has to continue to keep it a secret from him.
in the excerpt from act 1, nora agrees with helmer's ideas about borrowing and debt. by saying "as you , torvald." she pretends not to care about such problem, as if she has never borrowed money from anyone. in fact, regarding helmer's hypothetical death situation, she gives more importance to her loosing him than to the hypothetical debt. in this way, nora successfully draws his attention away from his worry.
b is my best guess. hope this : )