As shown in the picture, when Xiao Ming observed the propaganda slogan "Please turn off the lights at hand" with optical instruments, he saw the word "turn off the lights" and could judge its use.
As can be seen from the picture, the word "turn off the lights" looks like an inverted enlarged image, so the lens is convex and the slogan is between one focal length and two focal lengths, so A, B and C are wrong and D is correct.
So choose D.