Last and possibly least this afternoon, here is a worksheet on using gratis and gratuitous properly in English prose. This is a half-page worksheet with ten modified cloze exercises to guide students toward understanding and use of these words. They are both adjectives: gratis means “without charge or recompense” and free”; gratuitous, on the other hand, means “given unearned or without recompense,” “not involving a return benefit, compensation, or consideration,” “costing nothing,” “free,” and “not called for by the circumstances.” This final sense of gratuitous is the definition this worksheet deals with.
If you find typos in this document, I would appreciate a notification. And, as always, if you find this material useful in your practice, I would be grateful to hear what you think of it. I seek your peer review.