A conjunction (like 'and' or 'or') that connects two identically constructed grammatical constituents

• A. Idiom
• B. Coordinating Conjunction
• C. Utterance
• D. Agglutinative Language

Answer: (B)

The idea being tested is that a coordinating conjunction links two pieces that have the same grammatical form. Coordinating conjunctions like and, or, and but join two equal constituents—two nouns with nouns, two verbs with verbs, two adjectives with adjectives—into one larger unit. That’s why this option fits best: it describes the mechanism that connects identically constructed grammatical constituents.

For example, in "bread and butter," two noun phrases are joined by a coordinating conjunction, preserving equal structure. The other choices don’t describe this syntactic pairing: an idiom is a fixed expression whose meaning isn’t derived from its parts, an utterance is a spoken unit of language, and an agglutinative language is a morphological type, not a device for linking identical constituents.