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blood velocity is inversely proportional to the cross sectional area.
So when we have the smallest cross sectional area (the aorta) then blood is flowing fastest.
On the other hand, capillaries represent the highest cross sectional area in the circulatory system (each one is small but there are too many of them so collectively they represent the largest cross sectioanl area) then blood is flowing slowest which is in fact good to give time for nutrient (oxygen) and waste products (carbon dioxide) exchange.

However, be aware of the question telling you about a collapsed, shocked patient. In this situation the vena cava have the lowest cross sectional areas and therefore blood flows faster in vena cava than in aorta and faster in venules than in arterioles.
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