The evidence from the text which supports the prediction that Helmer will learn the contents of the letter are:
A. Helmer knows that there is a piece of mail from Krogstad in the box.
C. Helmer thinks that Nora is nervous and dismisses her pleas about the mail.
D. Mrs. Linde fails to find Krogstad so he can take back the piece of mail.
According to the given question, we are asked to show the evidence from the text which supports the prediction that Helmer will learn the contents of the letter.
As a result of this, we can see that based on the fact that Helmer knows that there is a mail in the box and he believes that Nora is hiding something about the mail, so we can predict that he would find out the contents of the letter.
Therefore, the correct answers are options A, C and D