简答计算机网络产生和发展的四个阶段

A．“Data”？means？information？about？facts.B．“Data”？means？information？concerning？numbers？and？statistics.C．Data？can？be？divided？into？primary？and？secondary？data？according？to？the？sources？from？which？they？are？collecteD．Secondary？data？refers？to？original？information？directly？collected？by？researchers？themselves.E．Primary？data？refers？to？the？information？borrowed？from？what？other？researchers？have？collected,？processed？or？stored？for？some？other？purposes.