Unless otherwise shown, what's the minimum headroom under bridges in the UK? Unless otherwise shown, what's the minimum headroom under bridges in the UK?

• Possible answers:

   
• A. 4.0 metres (13 feet)
• B. 4.1 metres (13 feet 4 inches)
• C. 5.0 metres (16 feet 6 inches)
• D. 5.5 metres (18 feet)