Explanation
Correct answer: C.
Choice C is the best answer. The convention being tested is the use and punctuation of an integrated relative clause. In this choice, the relative pronoun “that” is used to create an integrated relative clause that modifies the preceding noun phrase “a conceptual framework for pattern formation.” No punctuation is necessary between the noun phrase and the relative clause because the relative clause is supplying essential information about the framework.
Why the other choices are wrong
Choice A
Choice A is incorrect because no punctuation is needed between the noun phrase (“a conceptual...formation”) and the integrated relative clause beginning with “that.”
Choice B
Choice B is incorrect because it results in a confusing and ungrammatical sentence.
Choice D
Choice D is incorrect because it results in an ungrammatical sentence. A semicolon is used to join two main clauses or items in a complex series, and what follows “formation” is neither of these.