Final answer:
The eyelids are the structures that cause the eyes to blink. They protect the eyes and distribute tears.
Step-by-step explanation:
The structure that causes the eyes to blink is the eyelids. The eyelids are thin folds of skin that cover and protect the eyes. They help to distribute tears and protect the eyes from debris and foreign objects. When something comes close to the eyes, the sensory nerves in the eyelids send a signal to the brain, causing a reflex action that results in blinking.