Final answer:
Jem was worried that Atticus may have realized they were not engaged in any game at all on the night of the Radley's incident, rather than playing poker as they had claimed.
Step-by-step explanation:
The question refers to a scene in Harper Lee's novel To Kill a Mockingbird, where the character Jem Finch is concerned that his father, Atticus Finch, may have realized what Jem and his friends were actually doing the night of the Radley's incident. The correct answer is:
Jem thought Atticus may know that they were not playing any game.
Jem's concern arises from the realization that Atticus, being perceptive and intelligent, may have seen through their earlier deception. They had initially claimed to be playing poker, which was not true.