Mrs. Frisby and the Rats of NIMH (Open Court 4th) These vocabulary and spelling words are from the 4th grade Open Court selection, a chapter from Robert C. O'Brien's book. Each time the game loads you will be given a different set of 10 words. Visit Gamequarium, for more learning games and activities! Tools See a list of terms used in these activities. Matching Flashcards (Java / non-Java) Concentration Word Search This activity was created by a Quia Web subscriber. To learn how to make your own, just like this, click here.