If a creature says "whenever [this creature] becomes blocked by a creature" and is blocked by multiple creatures, how many times will it trigger?

When a creature has an ability that triggers "whenever [this creature] becomes blocked by a creature," it indicates that the ability will activate each time the creature is blocked. In the scenario where the creature is blocked by multiple creatures, each of those blockers is considered a separate instance of the blocking event.

Thus, the ability will trigger once for each creature that blocks it. For example, if the creature is blocked by three different creatures, it would trigger three separate times. This is because the rules of Magic: The Gathering recognize each blocker as a distinct event that satisfies the condition stated in the trigger, leading to multiple triggers rather than a single combined instance.

The other choices do not accurately reflect the rules governing triggered abilities in this context. Only one trigger would not account for the multiple blocking scenarios, and suggesting it only triggers with the last creature or not at all misrepresents how triggered abilities work when multiple conditions are met.