Which feature would be most useful for monitoring real-time data on campaign performance in Marketo?

The dashboard feature in Marketo is particularly valuable for monitoring real-time data on campaign performance because it consolidates various metrics and visualizations into a single, user-friendly interface. This allows marketers to track key performance indicators, view trends over time, and make informed decisions based on live data. Dashboards can display a range of performance metrics such as leads generated, engagement levels, and conversion rates, which are instrumental in assessing how well campaigns are performing immediately after launch or during their operational phase.

On the other hand, while the other options provide useful data points, they do not offer the same comprehensive, immediate view of campaign performance. Cost/period costs can help track spending but do not reflect real-time engagement or outcomes. Tags are useful for organizing and classifying assets or leads but do not provide performance metrics themselves. Emails sent can be an important metric to track but lack the broader insights into overall campaign effectiveness that dashboards provide. Thus, the dashboard stands out as the most effective tool for real-time performance monitoring.