Explanation:

- Option 1: "had better"

- Correct usage for giving strong advice or suggestion.

- Used to imply that something is necessary or urgent.

- ?? Correct Answer

- Option 2: "better"

- Incomplete without "had" for this context.

- "Better" alone doesn't convey advice.

- Option 3: "has better"

- Grammatically incorrect here.

- "Has" doesn't work with "better" in this phrase.

- Option 4: "are better"

- Incorrect structure for urging action.

- Usually denotes a comparison or improvement, not advice.