Answer: C. Time bombs
Time bombs are viruses triggered only by the passage of time or on a certain date. Some malicious software like viruses and worms tend to contain some logic bombs used in executing a certain payload at a planned time or just after meeting a condition. A time bomb is generally part of the computer program written to either start or stop functioning at a planned time. Time bombs are most often used in beta software when the manufacturer wants the beta version to be terminated after the final release date. With this, the user is forced to delete the software and get the latest version of it.