In Which of the Following Explanations Is the Explanandum Underlined

In which of the following explanations is the explanandum underlined?

A) I had to wear a different sweater, since I didn't have pants to match this one.
B) Due to the current strike, all classes will be canceled.
C) It was impossible to take a relaxing shower, because we were out of hot water.
D) No one eats at that restaurant anymore, because of its history of health code violations.
E) The legislation passed easily, since it appealed to the interests of both parties.