Explanation

The substitute teacher is speaking French in the wrong room and confusing everyone? Hilarious! Risible means “laughable” and is the only choice that makes any sense here. Note that arch can mean “mischievous, playful, roguish,” but is not appropriate here because the French teacher did this “accidentally.”

A risible.
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why not cursory, since it leads to a confusing state and there is no clue regarding risible situation

cursory means careless situation

here the teacher created a risible and laughable situation by picking the wrong classroom.

I do not see any possible scenario in which D is correct