Question

Read the passage below:

In her nineteenth-century studies of comparative avian anatomy, ornithologist Clara Hallowell resisted the prevailing dogma that neurological pathways governing bird song were entirely fixed from birth. While her contemporaries viewed these neural structures as immutable templates dictated by heredity, Hallowell argued that sensory exposure during early development rendered the central nervous system remarkably plastic. She demonstrated that juvenile finches isolated from adult vocalizations developed aberrant, simplified songs, whereas those exposed to heterospecific tutors modified their acoustic repertoires to incorporate foreign phrasing. However, Hallowell was careful not to overstate her findings; she emphasized that this neural malleability existed within strict genetic constraints, ensuring that species-typical syntactic boundaries remained unviolated. Thus, in Hallowell's framework, vocal learning was neither an unscripted acquisition nor a rigid execution, but rather a dynamic interaction between innate predisposition and environmental input.

In the context of the passage, which of the following choices most nearly expresses the meaning of the word 'plastic'?