What conflict does krogstad introduce? krogstad tells nora that he has written a letter telling helmer about her affair with the doctor. krogstad refuses to forgive helmer unless nora finds a way to come up with more money. krogstad tries to blackmail nora into getting helmer to keep him at the bank by exposing her forgery. krogstad plans to take helmer’s job managing the bank and ruin nora’s reputation while doing so.

The answer is:

Krogstad tries to blackmail Nora into getting Helmer to keep him at the bank by exposing her forgery.

In "A Doll's House," by Henrik Ibsen, Krogstad has lent money to Nora illegally  and secretly to pay for her husband's health treatment in Italy. As a consequence, when Torvald wishes to dismiss Krogstad from his job at the bank, the latter demands to Nora that she persuades her husband so that he can keep his job, and threatens to write a letter to Torvald revealing his wife's  fraud.