Explanation:

1️⃣ Process Flows (A)

Record-triggered flows can update records, which can cause triggers to fire again if the changes meet the trigger conditions.

Example: If a flow updates a field, it might trigger an after update Apex trigger unexpectedly.

2️⃣ Workflow Rules (B)

Workflow rules can perform field updates, which may cause an Apex trigger to execute multiple times.

Example: A workflow updates a related record, which triggers another field change, leading to a new trigger execution cycle.

3️⃣ Roll-Up Summary Fields (E)

Roll-up summary fields recalculate when a child record changes, which can cause updates on the parent record.

If an Apex trigger is monitoring the parent record, these updates can make it fire multiple times.

Why Not C or D?

C. Criteria-Based Sharing Calculations → Changes in sharing settings do not modify record data directly, so they do not trigger Apex executions.
D. Email Messages → Sending email messages does not modify records, meaning it does not impact trigger execution cycles.