operating systems

Which of the following are examples of "real time systems" An air traffic control system where, if a plane is detected a second late, it could result in a crash A business system where, if a customer's request is relayed to a customer representative a second late, the client could be lost A video playing system where, if the video pauses for a fraction of a second, the user will recognize this delay and be unpleased with the experience A set of data that have to be converted into reports overnight so that the reports are available by 9 am the following morning