Q.State which component of a time series (secular trend, seasonal variation, cyclical variation, or irregular variation) best explains each of the following:

Each part describes a movement with a different time signature — long-run and smooth, sudden and one-off, tied to the calendar every year, or wave-like over several years — and that signature is exactly what identifies the component.

1. A rise that is steady and long-term, continuing in the same direction year after year for a decade, is the definition of secular trend — it is not tied to any calendar period or business-cycle phase.
2. An unannounced power cut is a sudden, one-off, unpredictable event with no regular pattern and no way to have been foreseen or repeated on schedule — exactly what defines irregular (random) variation.
3. A pattern that repeats every year on the same calendar schedule (up every summer, down every winter) is, by definition, seasonal variation — the defining feature is that the cycle completes within one year and recurs.
4. A wave that takes several years (here, about seven) to complete one cycle, and is linked to the wider expansion/recession pattern of the whole economy, is cyclical variation — longer than a season, but still a repeating wave rather than a one-off shock.
   ✓Final answer

   (i) Secular trend (ii) Irregular variation (iii) Seasonal variation (iv) Cyclical variation.

Confusing cyclical variation with seasonal variation simply because both are 'repeating' — the distinguishing test is the length and regularity of the period (seasonal = within one year, calendar-tied; cyclical = several years, business-cycle-tied, not fixed to a calendar); and mistaking a sudden one-off shock (irregular) for a downward trend or a cyclical dip.