Explanation:

Let's examine the options for filling in the blank:

- Option 1: Lifeless

This word suggests a lack of energy or excitement. It doesn't fit well in the context of describing a role that communication plays.

- Option 2: Total

While this word denotes completeness, it doesn't quite capture the nature or importance of the role communication has in development.

- Option 3: Vital

This option means essential or of utmost importance. It fits perfectly as communication is indeed crucial for development.

- Option 4: Better

This word isn't appropriate as it describes improvement rather than the importance or function of communication.

Correct Answer: Option 3 - Vital

"Vital" emphasizes the essential role communication plays in development, aligning with the context.