ps. A third "split" that could have guided your process of eliminate was the "more research" v. "that more research." Since the non-underlined portion of the sentence states "researchers agreed that," a second "that" is needed to maintain proper parallelism.
曼哈顿官方:The first "split" I noticed was "preceded by" v. "preceded with." As one thing is preceded by another, eliminate choices A and D. The second "split" I noticed was "needed for determining" v. "needed to determine." Idiomatically, needed to determine is correct. Eliminate B and E. The best answer is C.
each 引导的独立主格 语义是colony 族群不是animals