Which of the Following Does Not Describe a Time Series

Multiple Choice

Which of the following does not describe a time series plot with an irregular cycle?

A) It repeatedly goes up and back down smoothly, but with an irregular pattern so as not to be predictable.
B) It randomly fluctuates with no pattern at all.
C) Its irregularity can often be explained by outside factors such as political or social situations.
D) All of the above.