Form a sequence that has two arithmetic means between -13 and 89.

Two arithmetic means create four terms, so there are three equal steps from −13 to 89. The common difference is (89 − (−13)) ÷ 3 = 102 ÷ 3 = 34. Adding 34 each time gives −13, 21, 55, 89, so the correct choice is C, “−13, 21, 55, 89.”

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