Compare two time series and choose the one which exhibits a more significant and well-defined trend, e.g., a clear directional movement (upward or downward) over time that is sustained across the series, with minimal noise, anomalies, or random fluctuations.

For example:
A time series with a steady upward trend, such as [10, 15, 20, 25, 30], would be considered significant and well-defined.
Conversely, a time series with frequent random spikes or drops, such as [10, 50, 20, 5, 30], is less likely to exhibit a well-defined trend.
A flat time series with little to no change, such as [10, 10, 10, 10, 10], would generally be considered to lack a significant trend.

Aspects that should NOT influence your judgement:
The source or origin of the time series data.
The length of the time series.
The order in which the time series are presented.

The time series may have similar characteristics, but you should still make a relative judgment and choose the label of the preferred time series.

[Option {label_a}]
... {text_a} ...

[Option {label_b}]
... {text_b} ...

Now you have to choose between either {label_a} or {label_b}. Respond only with a single word.