Which component of language is defined as the structure of whole sentences?

The correct choice focuses on syntactic structure, which is the component of language that pertains specifically to the arrangement of words and phrases to create well-formed sentences. This includes the rules that govern sentence formation, how different elements within a sentence relate to each other, and the hierarchical structure that determines the grammatical relationships among those elements.

Understanding syntactic structure is crucial because it helps explain how meaning is derived from combinations of words. For instance, different syntactic structures can lead to significantly different interpretations of the same words. This aspect of language encompasses aspects such as subject-verb agreement, the placement of adjectives, and how clauses interact within a sentence.

In contrast, morphology focuses on the internal structure of words and how they are formed from morphemes, the smallest units of meaning. Phonology deals with the sounds of a language and how they combine to form syllables and words. Corpus linguistics involves the study of language as expressed in large databases or corpuses of natural text. While all these components contribute to the overall understanding of language, it's the syntactic structure that specifically addresses the formation and organization of entire sentences, making it the correct answer to this question.