Final answer:
Time-series data may exhibit trend, random variation, seasonality, and cycles.
Step-by-step explanation:
Time-series data may exhibit several behaviors, including trend, random variation, seasonality, and cycles. In other words, time-series data can show a long-term upward or downward movement (trend), short-term unpredictable fluctuations (random variation), regular patterns that repeat over a specific period of time (seasonality), and longer-term repetitive patterns (cycles). Therefore, the correct answer is option 5: they may exhibit all of the above.