Assertion : Gill-lamellae in aquatic animals help in exchange of gases.
Reason : Each gill lamella carries many blood capillaries.

Answer

a

Explanation

Gills are the main respiratory organs of aquatic animals. Each gill bears rows of comb- like , soft , thin gill -filament, each gill - lamellace. Each gill lamella carries many capillaries. Water taken through the mouth , is made to flow from the pharynx ina single direaction between the gill lamella. blood flows in the capillaries fo gill- lamella ina direaction oppsite to the flow of water over the lamellar surfaces. this greatly helps in the gaseous exchange across the lamellar membrane between the capillary blood and the flowing water.