Final answer:
The statement that indicates an understanding of their child's illness is Option 2: "We understand that bulimia involves cycles of overeating and compensatory behaviors like vomiting or excessive exercise."
Step-by-step explanation:
The statement that indicates an understanding of their child's illness is Option 2: "We understand that bulimia involves cycles of overeating and compensatory behaviors like vomiting or excessive exercise." This statement shows that the guardians understand the key features of bulimia nervosa, including the recurrent binge eating and the compensatory behaviors that follow.