Option 1 -> Putrid means decaying or rotten, which relates to smell/condition, not duration.
Option 2 -> Invisible means cannot be seen, which relates to visibility, not time.
Option 3 -> Temporary means lasting for a limited time, which directly matches the meaning of ephemeral (short-lived/fleeting).
Option 4 -> Permanent means lasting indefinitely, which is the opposite of ephemeral.
Hence, Option 3: Temporary -> Ephemeral describes something that lasts for a very short time or is transitory in nature, making "temporary" the most accurate synonym among the given choices -> correct