What likely contributed to a 2.5-year-old showing signs of language delay?

Frequent ear infections can significantly impact a child’s ability to develop language skills. Persistent ear infections can lead to fluid buildup in the middle ear, affecting hearing and consequently hindering the child's exposure to sounds, language, and verbal communication. Since listening is a crucial part of language acquisition, any disruption in hearing can delay the ability to understand and use language, leading to delays in speech development.

In the context of the other options, although interactions with peers, exposure to books, and non-verbal communication preferences can also influence language development, they may not have as direct and immediate an effect as frequent ear infections. Listening difficulties resulting from ear infections can prevent children from hearing and learning language patterns, making this the most likely contributor to language delay in a 2.5-year-old.