Rule 383.3.e

Some Triggered Abilities will trigger “once each turn,” or “N times each turn.”

• 383.3.e.1 Such a Triggered Ability will only be performed the specified number of times each turn. If its trigger condition…
• 383.3.e.2 If the Triggered Ability says “you may” or “they may” as the first part of its effect, its controller has the choice…

Official Core Rules