What Difference Exists Between How CCTV Was Used in the Past

What difference exists between how CCTV was used in the past and how it is used now?

A) CCTV has been unable to capture every event and had huge blind spots but with new legislation has been implemented everywhere.
B) CCTV in the past was used to determine what happened after the fact, but it can be used in real time now.
C) It was a secret so it was much more effective before, but now terrorists use a small EMP blast to turn all cameras off.
D) Cameras were monitored by machines that identified threats but the government has outlawed that now.