The Difference Between Active and Passive Remote Sensing Systems Is

The difference between active and passive remote sensing systems is that

A) active systems involve the latest generation of satellites while passive systems use signals from older satellites.
B) active systems include aerial photography while passive systems rely on satellite imagery.
C) active systems can operate throughout cloud or fog cover while passive systems require clear sky conditions.
D) active systems emit their own energy while passive systems simply detect existing energy signals.