Please read this passage from the Article

Seward just had to have it for the United States. Plenty of people questioned why he would want to buy what seemed to be a useless chunk of ice. They called the deal Seward's Folly.


In this passage, the word folly means __________.


A. a wise idea or act
B. a silly idea or act
C. an affordable idea or act
D. an expensive idea or act