Explanation:

- The phrase "To err is human, to forgive divine" is a well-known saying. It implies that making mistakes is a natural part of being human, while forgiving is a more divine or virtuous act.

- Option 1: inhuman

- "Inhuman" refers to something that is not human-like, often cruel or lacking compassion. Errors are generally considered human, not inhuman.

- Option 2: human

- "Human" is the correct word that fits the phrase. Humans are prone to errors.

- Option 3: natural

- While making mistakes can be seen as natural, the phrase traditionally uses "human" to emphasize the human tendency to err.

- Option 4: blunder

- "Blunder" means a stupid or careless mistake. It doesn't fit well in the context of the saying.