Which pair represents complementary antonyms (no middle ground)?

Complementary antonyms are word pairs where the existence of one state absolutely precludes the existence of the other, meaning there is no middle ground or intermediate state. They are mutually exclusive and exhaustive. The correct answer, Alive / Dead, perfectly exemplifies this concept. An entity is either alive or dead; there's no state of being 'partially alive' or 'somewhat dead' in a definitive biological sense.

• Hot / Cold are gradable antonyms, as there are many degrees between them, such as warm, cool, or lukewarm.
• Similarly, Big / Small are gradable antonyms; objects can be medium-sized, quite big, or rather small.
• Tall / Short also fall into the category of gradable antonyms, allowing for average height or varying degrees of tallness or shortness. These pairs exist on a spectrum, unlike complementary antonyms.