C. lightweight metals and open-space structures for the wings would most likely be used by designers of ornithopters to mimic the bone structures of pterosaur wings. Pterosaur wings were made up of thin, lightweight bones with a complex internal structure, which allowed for both strength and flexibility during flight. Designers of ornithopters would need to replicate these characteristics in order to create functional wings for their devices. Using heavy metals would add too much weight and hinder flight performance, while wooden replicas and plastic replicas would not be able to replicate the complex internal structure of pterosaur bones. Therefore, lightweight metals with open-space structures would provide the necessary strength and flexibility while also keeping the overall weight of the wings relatively low.