Which field studies how sounds are combined to form meaningful units in language?

The correct choice, which focuses on how sounds are combined to create meaningful units in language, is morphology. Morphology is the branch of linguistics concerned with the structure of words and how they are formed. This includes the study of morphemes, which are the smallest units of meaning in a language. It looks at how these morphemes can be combined or modified to create words and convey different meanings.

While phonetics examines the physical properties of sounds in speech and how they are produced, it does not delve into the combination of sounds into meaningful units. Syntax, on the other hand, studies how words that have already been formed are organized into sentences, focusing on sentence structure rather than the formation of the words themselves. Sociolinguistics explores how language varies and its relationship with social factors but does not directly address the structural components of words. Therefore, morphology is the most appropriate choice when discussing the combination of sounds specifically to create meaning.