The boy is ill . . . . . . . . fever.

Solution (By Examveda Team)

In this sentence, "with" is the appropriate preposition to use with the word "fever." When someone is "ill with fever," it means they are suffering from or have a fever. "At," "in," and "about" are not the correct prepositions to use in this context.

Therefore, the correct sentence is: "The boy is ill with fever."