Which of these sentences is correct? 1: El perro era negro y energético, 2: El perro fue negro y energético or 3: El perro era negra y energético.

The correct answer is number 1. Number 2 is incorrect because it uses the preterite tense, which denotes a punctual, completed action in the past rather than a continual state of being. Number 3 is incorrect because it uses a feminine adjectival form, which does not agree with the masculine noun 'perro'.