A linguistic theory is constructed about what ______ is and how it works.
正确答案： C
本题解析：
语言的研究过程可以总结为：首先，要观察某些语言材料，从而发现一些共性并对其加以总结;其次，根据这些总结提出一些假设来解释这些语言材料，然后再通过进一步的观察来验证这些假设的正确性;最后建立一套语言学理论来说明语言的本质内容以及这些语言是如何发挥作用的。
Empirical studies show that the process of SLA is a process of constructing and modifying rules of communication.
Research findings have shown that language processing centers are situated in a single area of the left hemisphere.
From the sociolinguistic perspective, a speech variety is no more than a dialectal variety of a language.
The division of English into Old English, Middle English, and Modern English is nonconventional and not arbitrary.
Searle's classification of illocutionary acts is based on the classification of performative verbs.
According to the "principles-and-parameters" theory, "principles" refer to highly abstract properties of grammar which are applied to language in general and which generate phrases and at the same time restrain the power of Move a, while "parameters" allow general principles to operate in certain restricted ways, according to which particular grammars of natural languages vary.
Well-arranged sentences are considered grammatical sentences that are formed following a set of syntactic rules.