The ability to understand and convey meaning is primarily governed by what aspect according to language development theories?

The correct answer highlights the role of biological factors in language development theories. This perspective emphasizes that certain innate characteristics and neurological structures predispose humans to acquire language. Theories in linguistics suggest that all humans have a biological readiness for language; this is often referred to in the context of Noam Chomsky's theories, which propose that the ability to develop language is hardwired into our brains through what he termed a "universal grammar."

While other aspects like social context, environmental interaction, and cognitive processing certainly play crucial roles in how language is utilized and further developed, they do not fundamentally govern the innate ability to understand and convey meaning. Biological factors provide the foundation upon which these other elements can act, ensuring that while the environment and cognitive development can influence the specifics of language acquisition and use, the basic capacity to understand and produce language is rooted in our biology.