I would write, "the rest of the class has to guess which action this student is interpreting" which sounds more natural but your sentence can be understood.

The most clear way to write this sentence would be "The rest of the class has to guess which action that student is interpreting." or "The rest of the class has to guess the action that this student is interpreting." Because you used "which" right before the object "action", you do not need to include the article "the". Some other examples of this: "Which man" (correct) vs "Which the man" (incorrect). "Whch place" (correct) vs "Which the place" (incorrect). You also cannot say the "is" before action because it is already located at the end ("... is interpreting"). A way to detect this problem is to rewrite the section of the sentence Example: If you rewrote "which is the answer that this student is interpreting", you would get "This student is is interpreting which the answer". (incorrect) If you rewrote "Which answer that this student is interpreting", you would get "This student is interpreting which answer". (correct) I hope this helped :)

Thank you all it was very helpful!! =)

"The rest of the class guesses which activity the student is acting out." This is the game of "Charades," in which the players guess the actions that the other is pantomiming, or; expressing mutely by gestures.

Am I right to think " the action that this student is interpreting" means "translating, then acting out"?