After rising a short distance, the smooth column of smoke from a cigarette breaks up into an irregular and random pattern. In a similar fashion, a stream of fluid flowing past an obstacle breaks up into eddies and vortices which give the flow irregular velocity components transverse to the flow direction. Other examples include the wakes left in water by moving ships, the sound produced by whistling and by wind instruments. These examples are results of

• A. viscus flow at low speed.
• B. turbulent flow of air.
• C. streamline flow of air.
• D. laminar flow of air.