Explanation:

- The saying "_________ knowledge is a dangerous thing" is often used to warn against having limited understanding.

- Option 1: little

- "Little" suggests a small, insufficient amount.

- The phrase "Little knowledge is a dangerous thing" warns against having just a small amount of knowledge.

- ?? Correct Answer.

- Option 2: a little

- "A little" means some, but enough of something.

- "A little knowledge is a dangerous thing" does not fit the idiomatic usage.

- Option 3: few

- "Few" is typically used with countable nouns.

- It's not suitable here as "knowledge" is uncountable.

- Option 4: the little

- "The little" implies a focus on a small specific amount already known.

- It doesn't fit the phrase accurately.