The correct answer is "Helmer acts kindly towards Mrs. Linde while she is present, but insults her when she leaves".
In this excerpt we can observe very clearly the development of the conflict between Helmer's public presentation and the feelings he's hiding, which reveal themselves in his private life. Helmer's attitude towards Mrs. Linde is kind and warm when they interact, but once she's not present we learn that Helmer has a deep hatred towards her. This is a very clear case in which appearences are deceiving, as Helmer is acting the opposite way of what he truly feels towards Mrs. Linde.
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