What’s the use in running a true A/B test with experiments?

By letting marketers know whether or not a trial campaign drove user action that wouldn’t have otherwise taken place, it gives marketers a fuller understanding of user behavior.
By running simultaneous to an original campaign, a trial campaign controls for external factors, like seasonality, that might otherwise introduce bias.
By running individual campaigns one-after-another, an A/B test gives room for enough of a ramp-down period between tests that results can be decluttered.
By testing more than one variable at a time, an A/B test provides advertisers with information they can use to quickly adjust their campaigns.

The correct answer is:

By running simultaneous to an original campaign, a trial campaign controls for external factors, like seasonality, that might otherwise introduce bias.