Which sentence best indicates that "Object Lesson, Part 1" is a mystery?
A
"They're only patterning their behavior after criminals because they think criminals are strong, successful, and glamorous."B
"Class, this is Ellery Queen. I don't have to tell you who Mr. Queen is, and how honored we are to have him visit us."C
"An envelope with seven one-dollar bills in it was stolen, and from the way it happened the thief can only be someone in this room."D
"[W]hen I saw the money wasn't in the envelope, my first thought was exactly that, Mr. Queen. So I searched myself thoroughly."