Loading the question bank
Revision question · Road and traffic signs
Revision material from the imported DVSA bank includes source-checked Lanekind learning corrections. These corrections are not newly issued official examination questions, and practice does not reproduce a live test paper.

You won't be able to see any hazards that might be out of sight in the dip. As well as oncoming traffic, there may be cyclists, horse riders, parked vehicles or pedestrians hidden from view. Only start to overtake when you can see the road ahead is clear, giving you enough time to overtake safely.
Reviewed reading for this question