Final answer:
The statement about water supply in a dental unit passing through plastic waterlines and a control box that distributes to various attachments including syringes is true.
Step-by-step explanation:
The statement given in the question is true. In a dental unit, water is indeed supplied through plastic waterlines which then pass through a multichannel control box. This control box functions to distribute water effectively to various attachments used in dental procedures. These attachments include but are not limited to high speed hand pieces, air water syringes, and ultrasonic scalers. Each of these tools requires a controlled and clean water supply to ensure proper function and hygiene during dental treatments.