What signals or lights are used by controllers to indicate 'continue' to a taxiing pilot after a clearance?

What signals or lights are used by controllers to indicate 'continue' to a taxiing pilot after a clearance?

• A. A loud horn and waving hand.
• B. A red stop light to indicate proceed.
• C. A non-verbal thumbs-up from ground crew.
• D. Appropriately coordinated light signals or verbal clearance; typically the pilot will proceed as cleared.

Answer: (D)