In order for flow to separate A the boundary layer must firs

In order for flow to separate, A. the boundary layer must first have transitioned from a laminar boundary layer to turbulent boundary layer B. the boundary layer must first have transitioned from a turbulent boundary layer to laminar boundary layer C. the flow must be in a favorable pressure gradient D the flow must be in an adverse pressure gradient E. the surface must be dimpled

Solution

Flow separation occur when there is an adverse pressure gradient that is -ve pressure

Option D