A time series exhibits the pattern stated below. Indicate the type of time-series component described.
a. The pattern is “wavelike” with a recurrence period of nine months.
b. The time series is steadily increasing.
c. The pattern is “wavelike” with a recurrence period of two years.
d. The pattern is unpredictable.
e. The pattern steadily decreases, with a “wavelike” shape that reoccurs every 10 years.