Oral language is characterized as being:

Oral language is characterized as being spoken and heard rather than written. This definition emphasizes the nature of oral communication, which relies on spoken words and auditory processing. In contrast to written language, which is permanent and can be documented, oral language is transient and typically happens in real-time conversations. This immediacy involves a different set of skills, such as tone, inflection, and body language, which are not present in written communication.

The other options pertain to various other attributes of language but do not specifically encapsulate the essence of oral communication. While formal and structured or academic and complex styles may exist in specific contexts of spoken language, they do not define oral language as a whole. Oral language can include a range of informal and casual dialogues that do not adhere to strict structures or academic standards.