You can recall a cleared ECAM by pressing:

The correct answer is the RCL button. Pressing the RCL (Recall) button allows pilots to access a previously cleared ECAM (Electronic Centralized Aircraft Monitor) warning or message that was managed and acknowledged earlier during the flight. This feature is crucial because it provides essential information that may still be relevant for the aircraft's operation or safety, even after being cleared from the screen.

The RCL function effectively maintains situational awareness, enabling pilots to revisit critical alerts or messages that may have indicated underlying issues or even guided their decision-making process. This feature reflects the designed emphasis on safety and operational efficiency in the A320 system, ensuring that important information does not become entirely lost or overlooked after initial acknowledgment.

In contrast, other options do not offer the same functionality. Holding the CLR button for a specified time isn’t the standard procedure for recalling ECAM messages; instead, it's meant for clearing messages when they can be safely disregarded. The EMER CANC button is specifically used for canceling emergency alerts, and while it plays a vital role in emergencies, it does not serve to recall events. Finally, the ALL button is utilized for viewing all messages and warnings in a single list but does not perform the recall function for cleared messages specifically.