Identify the green circular structures indicated in the image. 
Definitions:
Chloropyridine
Refers to pyridine molecules substituted with one or more chlorine atoms, used as intermediates in the synthesis of pesticides and drugs.
Pyridine
An aromatic heterocyclic compound with the formula C5H5N, featuring a ring structure similar to benzene but with one CH group replaced by a nitrogen atom.
Nitric Acid
A highly corrosive mineral acid (HNO3) widely used in the manufacture of fertilizers and explosives, and in various organic synthesis processes.
Sulfuric Acid
A highly corrosive, dense, oily liquid acid, H2SO4, used in a variety of industrial processes like fertilizer production and in lead-acid batteries.
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