以下哪些变量可以用在 A/B 测试中？请选择三项

A/B testing involves comparing two versions of a marketing element to see which performs better. "Ad placement" (广告投放位置) is a common variable, as different placements can significantly impact visibility and engagement. "Target audience" (目标客户) is also crucial; testing different audience segments helps optimize who sees your ads. "Ad format" (广告形式), such as image vs. video or different headlines, directly influences ad effectiveness. "Delivery time scheduling" (投放时间安排) is less ideal for a direct A/B test because its impact is often intertwined with other factors and can be better analyzed through observational data or sequential testing rather than a simultaneous A/B split.