Choice "C" is correct. Compared to batch processing, real-time processing has the advantage of timeliness of information because data is processed and records updated immediately when a transaction is entered.
Choice "a" is incorrect. Auditing is normally easier with a batch system than with an online system. With an online system, it is harder, although certainly not impossible, to build effective audit trails. With less effective audit trails, it is more difficult to audit, and sometimes considerably different approaches to auditing (auditing around a system instead of auditing through a system) must be taken.
Choice "d" is incorrect. A batch system would normally be easier to implement than an online, real-time system. In a batch system, transactions would be sorted in master file order and then be processed against the master file in a single run. In an online, real-time system, each transaction is processed as it occurs so there must be controls in place to prevent transaction update conflicts when more that one transaction is trying to access a single master file. There are other complexities that would make an online, real-time system more difficult to implement than a batch system.
Choice "b" is incorrect. In general, a batch processing system is more efficient in processing large volumes of transactions than an online, real-time system. In batch processing, records are sorted in master file order to facilitate more efficient processing. In online, real-time processing, as each transaction is entered, the appropriate master file must be located and updated. The transactions would not occur in master file sequence so large volumes of transactions would usually be less efficient to process in online, real-time than in a batch processing system.