The correct form of decir for this sentence is "dijiste," which corresponds to addressing someone directly in the second person singular. It completes the sentence as: "¿Por qué dijiste tú que fue una lástima?" This choice accurately reflects the conversation context. ;
The correct form of "decir" to complete the sentence is "dijiste," making the sentence: "¿Por qué dijiste tú que fue una lástima?" This form is appropriate since it addresses the listener directly in the second person singular.
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