The financial hub of a business management information system (MIS) is accounting, the system of recording, analyzing, and reporting economic transactions.
Choice B is a run-on sentence. Choice C inserts an unnecessary which clause, making the sentence unnecessarily wordy. Choice D misplaces the modifier a system of recording, analyzing, and reporting economic transactions, which should be as close as possible to accounting. Choice E has awkward word order and the indirect and bulky phrase in that it is.