Final answer:
Lacy's response is consistent with the basic idea behind the development of sibling rivalry.
Step-by-step explanation:
Lacy's response is consistent with the basic idea behind the development of sibling rivalry. Sibling rivalry refers to the competition and conflict that can arise between siblings, often due to feelings of jealousy, attention-seeking, and a sense of unfairness in the distribution of parental love and resources.
In this case, Lacy feels that her little brother is getting all the attention and causing trouble, which is a common source of sibling rivalry. This can lead to negative emotions and a strained relationship between siblings.